what rupp said, i would pull a arms off, shocks off, swingarm off, and check and replace bushings and bearings as needed throughout.
depends if you want to put your money into chassis mods first, or motor upgrades.
nerfs are personal preference. since you mentioned them first i assume u like them. if you pick them up get good ones with built in pegs.
after that there is endless directions u can go on base chassis upgrades, but most of those will max out your budget so u may want to wait.
fmf is a decent low end pipe to compliment minor bolt on mods. begin with intake tract (carb reeds filter). if you want more mid top end u can upgrade to esr 5 pipe later (best all around pipe).
personally the first thing i would do is cr ignition, but they are hard to find and will eat up most of your budget, so you may want to hold off on that.