In my opinion, puff is all about implied pressure. You want to be just enough into someone's space to make them feel uncomfortable and provoke them into picking an option. A lot of the cast has tools that invalidate puffs approach options, and it's not uncommon to see a lot of low to mid level puffs deteriorate when their opponent can snuff out pound. For me at least, I didn't become decent with puff until I became comfortable with her tool kit. For the longest time I didn't even bother trying to use her normals because they seemed so stubby and useless, and I was too afraid to even try her rest combos. So, a big tip with puff is to just throw cold water on your face and just go for stuff, even if it might get you killed.
Patience in shield is a big thing with puff. There's so many safe aerials in this game that the cast is going to spam on your shield, so be mindful of that and know that nair isn't going to get you out of everything. I can't tell you how many times someone landed a safe aerial, anticipated a nair oos, and obliterated me.
Kass has a pretty decent youtube video going over all of puff's rest set ups, but as for some more obscure stuff, I think grounded pound is better than most folks give it credit for, it also two frames. Personally, I like to use D-smash to catch landing aerials because the lower profile throws off people's spacing, crouch in general is also really good for that.