Thank you for playing!
Some players have posted fusion guides you can use as reference, but the intended experience is to find the fusions by experimentation and chance. I would've loved to have every single powerup combine with another so that the chances of finding a new fusion are higher... but some combos made no sense and adding so many fusions would've required a loooooot more work.
There's no need to rush to find all fusions. You will eventually find them by playing normally. XD