This threads been dead for a little bit, but doing zombies can be fun. I think most of us are assuming that you dont have alot of track experience. If thats the case, I did the track school for my license my first year on my R1, luckily I was probably the slowest person on the track, and I couldnt bear the thought of wrecking it. I couldnt even, and probably still can begin to the use a fraction of the bikes capability.
I picked up an old zx6R for 500 bucks. I had to learn how to get the most out of the bike, exagerate good body position and learn the mechanics of racing rather than focus on dumping money into the bike.

I had blast on that bike, learned alot, and sold it for 1500 bucks after 2 seasons of beatings on it. (results not typical, some contents may have settled during shipping, etc...)
Cant go wrong with an old 600 or a 250 or an SV. any of those bikes give you something worth far far more than your entrance fees cover.......seat time.