I've only been shooting CAS for about 2 years and I'm still very much a new guy.
I was invited to a small club and found the members extremely helpful.
Everyone was willing to let me shoot their guns and "try them on for size". I was hooked immediately. No egos, no chips on shoulders, nothing to prove and lots of fun.
My second time out I just wore some jeans and a modern bandana (It's all I had). I already had three guns; a Ruger Blackhawk, a Winchester rifle and a double barrel shotgun. I was loaned another handgun, a Ruger Vaquero and I loved it. Went right out and bought me one the next week.
I got a LOT of advice on gun leather. Stay away from the cheap stuff was universal.
I went with a custom shop in San Diego Ca. and was very happy with what I got. It wasn't cheap but that was my choice.
While waiting for my leather to be made, I carried my guns around in a wooden box and NOBODY objected or laughed AT me. We all laughed TOGETHER about it but I was not made to feel I was doing things WRONG.
Costuming is a very important part of CAS/SASS matches. You can really go all out ($$$) or just keep it simple. Either way it's still fun. This brings in the concept of the "Spirit of the Game" where you try to immerse yourself into your cowboy persona. Again, some go all out, others are a bit lighter but are still having fun.
My wife enjoys the costuming almost as much as the shooting. it's something we both are having a ball doing together.
Oh, once the wife got the bug, she wanted specif guns and leather and she wanted them NOW!!! I've never bought 4 brand new guns in one month in my life. But she got her matching Vaqueros, 20ga SXS and Rossi lever rifle just as fast as you can imagine! I was thrilled to do it for her.
I'm on my second set of weapons myself. I've had two dragoons converted to cartridges and I have my eye on a new 1866 or 1873 lever rifle soon. New leather (can't have cartridge loops on a belt to hold up my dragoons LOL)
You're getting great advice from the others, If you have any specific questions you want to ask in private I would be happy to help out via PM but if you ask publicly, others will benefit I'm sure.
Good luck and have fun.