You received some good responses already. My slightly tongue-in-cheek response to your question "which guns should I buy" is NONE. Or more precisely, "nothing until you have attended a couple of matches to see and handle what is being used in competition".
It is not uncommon for new shooters to show up with guns that they have purchased, only to find out that what they bought is not well suited for the game. That can be an expensive mistake.
Go to the SASS clubs page and look for the clubs that are close to your area: http://www.sassnet.com/clubs/index.php
If you don't already have a cowboy shooting friend who can bring you to a match and mentor you, contact the match director for your local club and let them know that you are interested. They will probably take it from there.