I think @
strat61caster covered most of everything.
Bring some basic tools (your spare tire tool kit should probably cover it). Bring whatever else you feel you might realistically need. No need to overpack for your first time. If you need anything special or specific in a pinch just ask around. People will be happy to help.
Finally, when you are actually doing the driving, relax and practice looking further ahead at the track. AutoX can be pretty disorienting the first time since it's just a field of cones. However, they are laid out in a specific way. You can read ahead of time about the basics. They might also teach you in your class how to understand and navigate them.
My first time out, probably the only thing I did "wrong" was set my tire pressure too low. I had some economy/commuter tires, and the aggressive cornering combined with soft sidewalls caused wear on the sidewalls themselves (not good!). Luckily, the tires were already on their last legs.