I'm building, and I want to choose my CPU based on a GPU that costs no more than 200-250$ (I'm trying to spend the least possible, I don't mind sacrifices, if there's something that could do for less than 200, I'll opt for it, but if there's literally nothing decent in that range, I could do less than 300$) that is good/decent for gaming (1080p, I don't care about the newest titles), streaming, learning skills and applications like photoshop editing, video editing, blender, the adobe applications and whatnot.

I don't mind a used GPU at all, and I'd much appreciate to know what's the best CPU (used and new) to pair with that GPU.