they need to be relatable and before someone else does, make them about recent events. (you dont want repost police catching you and you actually thought of that meme yourself)
for example, the meme man guy going to fortnite.
you can say something about meme man going to fortnite and use that mario template where hes like
"THIS IS NOT OKIE DOKIE"
finding something new, yet relatable is kinda difficult but can get you lots of points.
try to skim the templates of users and of imgflip and find something in the news that was funny and put them together. that could help too.
...i love how i say all this and i dont ever do this myself lol...