There is actually a pretty nice 500r racing community. Most of them do not do anything more than simple power mods like exhaust, intake, and jetting. There are alot of suspension items out there though and one of the best mods you can do for overall performance is setting up the bike properly for your weight, I know a couple guys who race 500r's I'll see if I can get a site from them to help you out.
Well, a nice set of lightweight wheels will improve every aspect of performance on your bike, handling, acceleration, and overall feel. But they are gonna set you back $1700+ depending what you get. Do those basic mods you talked about along with some suspension mods and set up your suspension settings.
Yeah, but they make alot b***** difference than they do on cars. Marchesini forged aluminum wheels came stock on my 996 and I purchased Marchesini Forged Magnesium wheels for my RS250, by far the best performance mod I made. But if you are just planning on using the Ninja to learn on for a year or so and then sell it, it's not worth the investment.
Check out this bad boy, this is kinda overkill for what you are thinking, but you can follow suit on some of the suspension mods, maybe even the big bore kit if you plan on keeping the bike for a while....70hp at the rear wheel on that 500? You'd be embarrasing alot of b***** bikes