These are upgrades that provide large amounts of utility in every level.

Static Blast - Refreshing Jolt
Refreshing Jolt refreshing Jen's movement once after using Static Blast. As positioning is one of, if not the most important thing in this game, getting a second movement on a mobile character provides an immense amount of utility when synergised properly with other characters.

Swap - Friendly Refund
Friendly Refund fundamentally changes Swap, allowing Dall to endlessly switch her teammate's positions for free*. Friendly Refund is an upgrade that effects every member on the team, not just Dall.

*1 Mana is required to swap, but is refunded immediately afterwards.

Transference - Genius Grant
Genius Grant turns Transference from a 1 time use long range kill or damage prevention, into a potentially infinite use, map clearing machine. Using Genius Grant to its fullest potential requires thinking about Transference as a main weapon, not a side utility. The lack of action or mana cost on Transference allows Genius Grant to come into play several times per turn if necessary, while not getting in the way of any of Bank's other abilities.

Using Genius Grant I was able to kill The 50 clone Liv from Liv and Let Die who appears at the end of Medil Proving Ground

These are upgrades that transform character abilities and provide large amounts of utility in most situations.

False Prophet - Persistent Delusion
Persistent Delusion provides Zan a mana refund for prophets that die before naturally despawning at the end of the forsee phase. This essentially removes the mana cost from most prophets if used correctly. Prophets can even be used as targets for abilities like Chain Bolt or Static Blast with Refreshing Jolt, then used for another purpose thanks to the refund

Persistent Delusion is S Tier when combined with Dall's Swap - Friendly Refund and Charge - Rampage II which allows Zan to use his prophets as Charge targets for Dall, allowing her (and the rest of the team) to get to practically any position on the map.

False Prophet - Useful Fiction
Useful Fiction allows prophets to interact with objects they appear next to, such as reinforcement doors, intel pickups, laptops, turret control panels, and more. These actions all provide Zan with +1 mana when completed, allowing another prophet to be created after.

Useful Fiction is S Tier when combined with Dall's Swap - Friendly Refund and Swap - Blind Faith upgrades, allowing Dall and Zan (and the rest of the team) to quickly take over and interact with most/all of the map on turn 1.

Static Blast - Point Blank
Knockback is Jen's bread and butter, and being able to double the knockback on her basic based on positioning is very strong. Useful for moving steady targets like heavy gunners, or providing the extra damage needed on a 3/4 health enemy.

Chain Bolt - Strong Finish
Just like Static Blast - Point Blank, the extra knockback at the end of Chain Bolt adds a useful bit of both damage and utility.

Gale Grenade - Second Wind
The Gale Grenade is already a great ability, so adding a multi-target movement refresh just adds another piece of mobility onto an already stacked kit, this time affecting more than just Jen. The only downside is the limited use of Gale Grenades.

Sedative Cocktail - Stings
Stings adds some much needed direct damage to Banks' kit which isn't dependant on mana.

Death's Door - +1 Use Per Encounter
Pushing an enemy into Death's Door is an instant kill for 99% of enemies in the game, so doubling the amount of instant kills on the team is a no-brainer.

+1 Use Per Encounter is S tier when combined with Death's Door - Death's Floor, doubling the amount of map-wide teleports on the team.

Charge - Rampage II
With Rampage II, Dall get's her action refunded whenever her Charge hits a target. Even without other upgrades, this ability synergises incredibly well with the rest of Dall's kit as Swap allows Dall to place herself into a position for another charge, and Throw Riot Block allows Dall to place a target to charge at anywhere in her path.

Swap - Swap With Objects
Swapping with objects doesn't just make Swap more versatile on levels with many objects on them, it also improves Throw Riot Block, giving Dall the ability to swap to anywhere in view by throwing the riot block there first. It doesn't just improve Dall's positioning though. It also adds the ability to move environmental hazards in range of enemies.

Impaling Vine - Gripthorns
As stated before, positioning is key in this game. While the additional movement range of 3 tiles may not seem like much, it can prove incredibly useful and gives Rion a use for his action on rounds where he can't use Impaling Vine on an enemy.

These are upgrades that provide some benefit most of the time, or large benefits occasionally.

3 Bolt Burst - +1 Damage
Extra damage is always appreciated, especially on a basic attack. +1 Damage ranks at a B due to providing a minor buff that applies at practically every point of the game.

+1 Damage is A Tier when combined with 3 Bolt Burst - Supportive Fire II as the extra damage will quickly add up with each of Zan's assists

+1 Damage is A Tier when combined with False Prophet - Hurtful Lie as each prophet's attack will benefit from the increased damage

+1 Damage is S Tier when combined with both of the above upgrades, turning Zan and any prophets he's summoned into a firing squad that assist on every basic with extra damage.

3 Bolt Burst - Supportive Fire II
Supportive Fire II allows Zan to assist on every basic attack, not just once per round, allowing Zan to provide large amounts of bonus damage to the team.

Supportive Fire is A tier when combined with False Prophet - Hurtful Lie as all of Zan's prophets gain the ability to assist on every basic attack.

False Prophet - Hurtful Lie
Hurtful Lie gives Zan's prophets the ability to use Zan's basic attack on the closest target when they spawn. Unfortunately this ability is brought down by the inability to choose the target.

Hurtful Lie is A tier when combined with 3 Bolt Burst - Supportive Fire II as all of Zan's prophets gain the ability to assist on every basic attack.

Static Blast - Refreshing Jolt II
It might seem strange that the ability to refresh movement once ranked higher than the ability to refresh it infinitely, but it ranks so far below the prerequisite perk as it's difficult and often expensive to get enough action refreshes to really make it worthwhile.

Chain Bolt - +1 Target
Chain Bolt is a useful ability for damaging and moving enemies, triggering environmental hazards, and even moving teammates. The knockback on Chain Bolt is determined by the angle it hits its target, and allowing an extra jump in the chain allows more control on these angles.

+1 Target is A Tier when combined with Chain Bolt - Superchain, as the amount of extra targets is doubled.

Chain Bolt - Conduits
Action points are hard to come by, so abilities that grant or refresh them are great additions to the team. Unfortunately Chain Bolt can be a difficult ability to use on an ally in a non-obstructive way.

Sedative Cocktail - Drowsy
Turning up the poison on Sedative Cocktail technically adds an extra, stackable, 9 damage per turn. Of course, it's incredibly rare that all 9 tiles of the attack land on an enemy, but the extra damage ramp-up is still incredibly powerful, especially as it bypasses shields and armour.

Sedative Cocktail - Lightheaded
Banks has many uses on the team, and adding even more unsteady to her kit, especially to her basic, synergises with everyone on the team. The only thing dragging it down is the fact it only applies to the target in the centre of the blast.

Spectral Skull - +1 Damage
Spectral Skull's initial 2 damage is ok, but enemies don't stay that weak for that long. If you're good with aiming the skull too, then the extra damage really starts to add up.

Spectral Skull - Dizzying
As basic attacks and Spectral Skull both use actions, it can be annoying to miss out on the debuffs applied by Banks when you use Spectral Skull. With Spectral Skull applying unsteady though, and likely to more targets than Sedative Cocktail could hit, sometimes Spectral Skull is the better option.

Charge - Momentum
Extra knockback is almost always a good thing. In Dall's case, there's no almost. Most situations provide enough room to make use of the 3 tile minimum too, though there are certainly times where the room isn't available, and that knocks this upgrade down to a B.

Charge - Rampage
Unlike Rampage II, which turns Dall into a charging machine, throwing enemies all around the map, Rampage only lets Dall take 1 extra action per turn. While it may not allow for excessive charging, it does allow for a hit and run, or following up a Charge with a Censer Slam.

Charge - Telephasing
Telephasing allows Dall to charge right through most obstacles in her path to charge at her true target. While the opportunity to use it doesn't come up too often, you don't want to be caught without it.

Impaling Vine - Frostfingers
Rion's brittle debuff is great for dealing with many tougher enemies in the later parts of the game. Adding a second method to apply it, especially on a basic ability, is very powerful. As the brittle applies after the damage, it also makes stacking it easier by using Impaling Vine first.

Impaling Vine - Quicksprout
The ability to reposition teammates is great, though held back by the necessities of line of site, and the limited control over their movement.

Brittling Dart - Corrosive
A simple upgrade that synergises extremely well with Banks. Very useful on tougher enemies with gas masks as it allows Banks poison and unsteady to affect them much sooner.

These are upgrades that provide occasional, medium amounts of utility.

3 Bolt Burst - Supportive Fire
A single assist per turn doesn't provide much other than a nice surprise. Trying to use it at a specific time can prove to be more effort than it's worth. Necessary for Supportive Fire II though.

Time Boost - Time Bomb
Time Boost is a great ability, but unfortunately the upgrade doesn't provide much value due to only working in a small area. With careful positioning of your team, you can get extra value out of the upgrade, but typically not much more than 1 extra person affected.

Predictive Bolt - Conviction
On its own, Predictive Bolt isn't an immensely useful ability, and the upgrades for it don't really change that. With the use of other character's abilities, this upgrade could be used to deal decent amounts of damage to multiple enemies, but in most situations there are better, easier options available.

Predictive Bolt - Validation
Mana generation is useful, especially on Zan, but Predictive Bolt isn't the easiest way to do it.

Validation is A Tier when combined with Dall's Swap - Friendly Refund as Zan can set up Predictive Bolt, then Dall can swap him into position to hit an enemy with it, getting the extra mana.

Broom Breach - Forced Entry
Forced Entry opens up a few extra entry points for Broom Breach, though they're rarely really required. The knockback is decent, but not enough to often deal enough damage or knock through another window, except on narrow maps.

Gale Grenade - +1 Use Per Encounter
The Gale Grenade is a pretty useful tool, and an extra one is always appreciated. Unfortunately, Jen just has better upgrades available.

Spectral Skull - Big Head
If you find aiming Spectral Skull difficult, this upgrade might rank higher for you. It also allows the skull to hit more targets, though this can include teammates which are also damaged by the skull (possible bug?)

Death's Door - Intercept
It's not always possible to knock an enemy directly into Death's Door, so turning the square in front of it into an instakill makes it much more accessible. These situations are decently rare, though it's very nice to have when they come up.

Censer Slam - +2 Damage
Censer Slam already does a respectable 3 damage and 1 knockback. While the extra 2 damage does turn this attack into a monster, I find myself rarely using Censer Slam, except to finish off weak enemies after my final charge. Dall also just has better upgrades available.

Throw Riot Block - Recall
The riot block has its uses, and those uses often end up getting it destroyed, so being able to replenish it is quite handy. Unfortunately Dall just has better upgrades available and not many points to go around.

Rabid Bite - +2 Sedative
Adding a strong poison to Rabid Bite is both a blessing and a curse. It makes your rabid enemy, often a stronger enemy, easier to kill when everyone else is taken care of, though it also means your rabid enemy might die too soon.

Spore Bomb - +1 Use Per Encounter
Spore Bomb is a decent throwable on its own, so an extra one is alright.

+1 Use Per Encounter is A Tier when combined with Spore Bomb - Intelligent as allies can now easily add to the damage of Spore Bomb while avoiding getting hurt, making Spore Bomb a much more useful utility.

These are upgrades that provide very minor/very rare amounts of utility.

Predictive Bolt - +1 Damage
Predictive Bolt already does a solid 4 damage. While this allows Predictive Bolt to kill any enemy with 5 effective health now, it's often not worth the amount of effort to get Zan in position to use it.

+1 Damage is B Tier with Predictive Bolt - Conviction and Dall's Swap - Friendly Refund and Swap - Blind Faith upgrades as Predictive Bolt becomes a lot easier to use, and the extra damage helps trigger Conviction.

Gale Grenade - Storm Grenade
The two damage provided by Storm Grenade only affect the centre tile, and is useful so rarely that it is absolutely not worth the point compared to any other upgrade for Jen

Transference - Overreaction
Banks has enough methods to apply unsteady in her kit. It's not worth using a Transference charge to apply 1 overreaction, and Banks has better upgrades to spend points on.

Swap - Panic
While making enemies commit friendly fire can be nice bonus damage, I found this upgrade actually occasionally worked against me. Added with the fact that Dall has many better upgrades to spend points on, I don't recommend Panic.

Spore Bomb - Pressurised
This is a tricky one. I've placed it in D under the assumption that the knockback affects allies when you don't have Spore Bomb - Intelligent, though I can't prove it. Other than that, I find that any Spore Bomb that would be doing large amounts of knockback is already doing sufficient amounts of damage to kill anyone caught inside it.

For upgrades that provide no or negative value.

Throw Riot Block - Wall Mode
While Wall Mode itself provides barely any value, it actually harms you by using a perk point that could be used for any of Dall's other, superior, upgrades.

Again, these are my personal opinions. If you disagree with any rankings, please leave a comment below and you may change my mind. These rankings may change in future as I experiment with different combinations too.