My first track bike was an under powered (for the class) Triumph TT600, it had great handling, had good brakes and the motor was pretty mellow for a 600. The best part about that bike was that I could throw it down the track without losing sleep over it. I ended up dropping that bike twice on the track. The second time ended my time with that bike.
I then moved into a 2003 636, it was a bit pricier than the TT600, but not so much a crash would upset me. I rode that bike for a year and didn't crash so I thought it was time to move into a newer bike.
I got a 2013 MV Agusta and proceeded to crash it my first track day on it.....
But then I rode that bike for a year and a half more without crashing.
Now I am on an RSV4 that I have been having great success with.
The moral of this story is if you are new to track riding, having a bike that is cheap enough you can throw it away takes some of the stress out and just lets you focus on riding.
I would advise you to buy a bike that is already track prepped. The 300s are cool, but I have some friends that just dumped $15,000 into their R3s (including purchase of new bike). This is an extreme example of how expensive building a bike can be, even a 300! WERA
is a great place to find used track bikes for a reasonable price. Look for 250s, 300s, SV650s or even a 600 that are already built, you will save a bunch!
Hopefully at some point in my rambling, incoherent response there was something close to anything that could be considered a rational thought. Hopefully no one in this forum is now dumber for having read to it. I should get no points, and may God have mercy on my soul.