welcome to the site man..
basically, its how much do you wanna spend. the mods you can do are endless.. here are a few common ones that will turn your banshee into a whole other machine.
1)aftermarket pipes..depends on your riding which kind you buy.
2)aftermarket reeds
3)aftermarket air filter..stock is junk.
these are probably the 3 most common mods. they will offer you the most bang for your buck. give us a budget, and we can get you set up...
also, im not sure what premix oil youre using, but klotz is a good oil to use. im guessing if you bought it brand new the stealership recommended yamalube.. well, that shit is junk. switch immediately..