Adam,

Enduros are by far the best bang for the buck! You'll enjoy them because a lot of times the fastest car doesn't win.
In SEDIV ECRS, you are required to have a 5 lb (min) fire extinguisher, and a bag of oil dry/kitty litter in your pit as a minimum safety requirement. Check the supps for anything else they might require.
There are a thousand things you CAN bring to your pit, you'll probably learn the hard way what you'll need like the rest of us
I started with 2 tires, a jack, jack stands, torque wrench, duct tape, tie wraps/zip ties, oil, windex, paper towels, FLUIDS for drivers/crew, a basic toolbox, and a big hammer or an aluminum baseball bat (for prying fenders away from tires-just roll and go).
There are a bunch of others, just make sure all of the safety requirements are met, as that is the number one thing that will keep you and your crew out of trouble.
Make friends with your pit neighbors, as most people will lend you anything you forget, and make mental notes of what else you'll need to bring next time.
Good luck!
"To finish first, you must first FINISH"

Mark