I agree with hipwr223, just jump in with what you have the first time.
Get some decent ammo and work up some zeros for 200, 300, and 600 ahead of time if at all possible. If not, just make sure you have a good 100 yard zero and someone will help you come up for the rest.
You will need a sling and glove. A coat is nice to have and without one you will get beat up, but you can decide after a match or two if you are going to stick it out.
If you have a decent spotting scope and stand, I would bring that too. A shooting mat helps keep you off the dirt in sitting and prone, but almost anything would work including a carpet scrap.
Two good 20 round magazines and a BobSled will complete the minimum kit. The two mags are required, the sled is good for the single feed slow fire stuff such as the 200 standing and 600 prone, for example.
Try someone's hardback coat and dry fire at 200, you will see why you need one later.
Good luck, I hope you turn on and jump in!