Great to see that you are considering entering the dimension where your car will really come to life!
In addition to the replies already made to this posts as well as the many past threads that you should be checking out, I would highly recommend to take a Track specific insurance, like the one offered by the BMW CCA organization through LocktonAffinity (see under
www.bmwcca.org). Yes, accidents are very rare, but what if? In the big scheme of things, $300 dollars are not much...especially if something happens.
For the rest, no need to overdo it when it comes to helmet, special gear, etc...
Be safe, have fun and learn a lot! I know I did recently at Lime Rock Park with BMW CCA!!