Re: First track day question.
I've been asking this very question for a while now, getting a lot of good feedback from local track day warriors.
General thought is, any sport bike tire will be sufficient for your first couple track days. You'll be learning the track: brake points, apex, getting comfortable on the bike, suspension adjustments, etc..
I just bought a set of Bridgestone S21 for my bike. I'm planning on splurging on some nice Supercorsas once these wear out.