If you are going to the track for the first time... I would NOT spend any money on "upgrades", merely buy a set of decent street/strip pads, and a spare set of rotors. Go out, have fun, and if it is something you want to continue to do... spend your money when you need to. I ran for two years on stock brakes.
If you want a good read. Browse my thread on "tips for taking your 3000GT/Stealth to the track".
http://www.3si.org/forum/showthread.php?t=306660