+1, start mimmicking/making what you want to make. You’ll bump into issues and that’s where you will learn. gogogogogogo
For example, just mimmick an effect like this with some spark and smoke particles (I don’t know how experienced you are so maybe you’ve got this down already)
Since you’re asking, I’d say start with materials and particles. Those are the base foundation of FX. Houdini and destruction sims are an additive thing on top of that. Again, I don’t know where you are in learning FX but start with basic particle work.