Steven the bare minimum is a cap revolver and flintlock pistol to get classified. If you only show up with one pistol and talk to the people there they will help you out to get you started. The pistol shooters are a great bunch of people and will be glad to get you started. Here is a link for the NMLRA spring shoot and also on that page is a PDF of the rules.
If you get a good kentucky percusion, kentucky flint and percussion revolver. You can shoot all the events except the optical. Adjustable triggers and sights are nice and as you shoot more you will see what you need to get better scores. Good luck maybe I will see you there. :v
You can use any caliber. most people like the smaller calibers because of the recoil beining reduced and follow through with lighter loads is better. I have 2 50 cal kentucky styles that I use for the kentucky shoots and I like them. :hatsoff: