The best pranks are easy ones that you don't have to put a lot of work into. One that I think would be a great prank is to paint some clear nail polish on pencils or cover a bar of soap. There are a lot that could be really fun to do.
Maybe one of these articles can help you out!
https://www.boredpanda.com/pranks-april-fools-day/
https://imasterplaster.com/funniest-pranks/
https://www.persil.com/uk/dirt-is-good/celebrations/10-fun-simple-april-fools-pranks-for-kids.html