Oh, those aren't dumb questions at all!
I'm using custom sprites I made for the heroes (but not things like that boulder--save for my boulder edit for when the boulder is submerged in water), custom monster designs, my own music I composed, dialogue is all mine, but things like tilesets are either from other creators who allow their work to be used in others' games or the already made tilesets that come with RPG Maker MV.
And yeah, it's a great tool to get the basics of game creation, but also something that can be rather complicated depending on what one is trying to set out to do.
