This is actually pretty easy. If you're a newbie (rookie, new racer, noob) you should bring everything that you used to build your car/truck. Tools, tape, scissors, etc. EVERYTHING you used. Odds are, you don't have that much stuff. From that point on, if you need to borrow a tool TWICE, you need to buy your own. (because I'm not borrowing you mine anymore, I'm not the Snap-On man)

Once at the track a couple of times you will see and experience what tools are NEEDED and what tools would be nice to have. Allowing you to make educated purchases in order of necessity. "Do I need a nice set of quality hex tools, or do I need a fancy pit light?"