http://www.ft86club.com/forums/showthread.php?t=25485
imo track it stock, aero is of minimal performance benefit to the average HPDE goer (aside from looks) and burn up the stock tires (you already paid for them and they are very durable in my experience) and do tons of reading before buying.
KISS applies here: keep it simple stupid. Messing around with aero settings, swapping tires, figuring out pressures and settings can be huge distractions taking away from what newbies should be doing: having fun and learning.
Budget for brake pads and fluid, on my second track day I fried the oem pads and boiled the fluid and was driving home with a spongy sketchy pedal. Depending on your skills you may be perfectly fine on OEM brakes for the first track day, but if you're comfortable at all with hard braking (actually utilizing the ABS) you'll probably use them up really quick. There's lots of threads on brake pad selection and different fluids that can be found.
http://www.ft86club.com/forums/forumdisplay.php?f=39
Here's a recent thread, while hybrid pads were bypassed for this discussion they may be a good place for first timers to reduce the risk of brake fade for your first few outings.
http://www.ft86club.com/forums/showthread.php?t=94284
Other than that read read read and take every opinion with a grain of salt.
Edit: Like this one below 
I believe I had a relative try PS AS3's, I think he destroyed them with a single day of autocrossing, heavy car with a big motor and a lead foot didn't do them any favors but when choosing tires they haven't come up on any short list I've seen. Again read read read everything you've asked has been answered by 100 different people in 100 different ways on this forum alone.
Don't forget to have fun
