First off, welcome to the sport. One you get bitten, you're not easily cured!
+1 (as always) to Sir Charles and Shotgun Franklin. They give excellent advice. Even though not enough Cowboys follow that advice.
Take what gear you have (forget the rest) and GO TO A LOCAL SHOOT. Franklin was right about bringing your own ammo, but even that's not really necessary, especially on your very first shoot. JUST GO!!! I guarantee you'll get more than one Cowboy offering his guns for a trial run and test drives are the
best only way to figure out what guns fit you and your style.
For example - I didn't follow this advice as well as I should have, and my entire first set of guns was wrong. I ended up passing those guns onto my son and had to buy an entire new set once I figured out what fit me. DO NOT repeat my mistake.
Also, since nobody mentioned this, look into reloading. It's really the only way most people can afford this sport. An average match will use 2 boxes of ammo and 1 box of shells. Reloading will cost a fraction of factory ammo, and if you cast your own lead, its' even cheaper still. I save about 80% on my costs by casting and reloading.
Finally, regarding gunfighter - it's all muscle memory. If you shoot one-handed (Duelist), you halfway there. This may sound crazy, but if you're set on Gunfighter (and I say go for it) and you don't have access to 2 revolvers, go grab a pair of dollar store cowboy cap guns. As long as thy have a hammer and a trigger, they'll work. And just practice with those. You need to train your hands to cock one while shooting the other. It's all muscle memory.
This is also true with all your guns. Most of this sport is practice. Not just shooting, but loading, drawing, transitions, etc. You need to train your hands how to do all that without even thinking it.