It's a big pasture you're riding into...
Since you've bought a shotgun, I'm guessing that you're more than just a little interested.
With a shoot tomorrow, take what you own and a couple boxes of 45 Long Colt cowboy ammo. If the club is like most, you will have a chance to shoot all the types.
I'll just throw out a couple of ideas here. If you don't reload, 38/357 is much cheaper than 45 LC. 45 LC is more reliable loading into rifles (especially 92s). If you fall for the game, you'll probably start wanting the more unique choices: Yellowboys, 1875 outlaws, Richard Mason conversions. Rugers are excellent, durable revolvers, but lack variety. Look for "featherlights" to shoot in your shotgun.
Take your time collecting your clothing. Shop "Goodwill/thrift" type stores and get some basic shirts. Buy quality leather and you'll only have to buy it once.
Best of luck...Welcome to the fire, amigo.
You might try
www.sassnet.com for more information.