Ok, so being funny in Quiplash is quite hard, because you actually need some brain power to write funny stuff .. or you just write "♥♥♥" or something with "penis" in every card. Believe me, "♥♥♥" is the ultimate power play in this game and I 100% guarantee it to work. (I DO NOT take responsibility if this doesn't work.)
A good example:
I advise you to use this method of playing, because ♥♥♥ and ♥♥♥♥ funny haha, but if you're a comedic mastermind and opened your third eye and unlocked all your chakra points, you're probably ready for THE ULTIMATE FUNNY, which is pretty hard to explain, so stick with me. So when you get your prompt, you basically have to follow this image:

That should cover Quiplash.

Tee K.O. is much easier to master, so it's possible to learn for normal mortal people, who haven't opened their third eye yet, so listen:

The drawings:
The drawings are easy and you don't necessarily need drawing talent, but it helps quite a lot.
Your drawing either has to be something random or an insider in your friend group.
It needs to be really clear, with what it is, so you shouldn't go too much in detail, in other words, everyone should instantly get what you've drawn. Memes like Peter Griffin, Minions or Sans are also pretty good, when it's accompanied with a funny caption.

The captions:
You could use the first technique, which I told you in the Quiplash guide, but that gets boring pretty fast, so I advise you to use basically the same technique as in the drawing part: insider, random stuff and MEMES.

Your T-Shirts:
To make the best T-Shirts, you have to know the people you're playing with, so you know their type of humor. If the drawings or captions, that you get, are bad, you're ♥♥♥♥♥♥ and basically lost, but if you're lucky you'll get some funny ones, but don't get ahead of yourself and observe which combination of drawing and caption is the funniest.

Here are some examples: