Want a wish list, check out the link in my signature...
Seriously though, best thing to do...
Sprockets (-1,+2) or +1 in the rear, maybe 520 conversion why you are at it.
Something with or for the exhaust, race baffles w/gutted cat, slip-ons, full system, makes a far better note
New tires, get something sticky for the twisties... Bridgestone 003RS, Corsa III, 2CT, etc
HID headlights, simple $60 mod, much better night time riding and visibility
Stainless steel brake lines and better brake fluid, increase the stopping power
New brake pads (Vesrah SRJL or C.L. SBK5)
Correct suspension springs for your weight, maybe some new internals for the forks
Tweak your suspension based upon Sport Riders settings, or have a professional do a setup for you.
PCIII, PCV, or Bazzaz if you do a full exhaust
Smog block off plates or plug the system and remove it (this could be free)
Motivation frame sliders
There are a ton more, but for around $2K, you could do all that...