What should I buy??

the banshee...LOL! do you expect us degenerates to suggest a 400 4 poke? maybe a 450 though. haha
 
Booo, a fellow 2stroker recommending a 4 poker. thats it, the world is now Over!!! lol

What? a 250r is a 2stroke, Either way if its for track I would say a 250r as well, guess you could get a shee but its probably not going to have the best track manners. For all around fun and enjoyment go with the shee
 
If you wanna rip the track and you're on a budget, trx250r and lt250r are the way to go. And there's 2 free easy front end mods you can do to the lt so it handles as good as the trx. A blaster ain't a bad choice either if you wanna have a good time on the track.
 
I know I'm going to get hated on for this but seeing you already have a Blaster,a z400 could be nice to have. There not as fast as a 2 stroke but there's more to ridding then max power.