CAS is a **four** gun match unless your club has a Traditional Cowboy Division. You need two sixguns, a lever action in a pistol caliber - it doesn't HAVE to be the same as your sixguns, but it is convenient on ammo - and a shotgun; either double barrel (hammer or hammerless but no ejectors) or hammer pump.
CAS folks are very helpful. Go ahead and go to a shoot even if you don't have all four guns; there will be plenty of nice ones offered to you for the borrowing.
Another SAA clone, a Navy Arms '92 clone, and a Stoeger/IGA double would be about the least expensive rig. There are CAS gunsmiths who can turn them into 19th century raceguns. They take care of the broken spring horror stories by putting in a coil spring and plunger for the hand (many Italian clones are coming in with them factory installed) and a piano wire trigger/bolt spring.
Belt and holsters, period wardrobe which can be as simple as jeans, plaid shirt, hat, and boots. You will tend to accumulate Stuff. A kid's red wagon with a gun rack is ok and cheaper than a purpose built gun cart.
Go to
http://www.sassnet.com and check out the information there. Get on the SASS Wire and swap yarns on their board.
Mainliest thing is to be thinking up an Alias. You must have one and with 40,000 members, you will have to be original.
Uncle Jim
SASS #3879