I would also suggest shooting production where everyone shoots minor, usually 9mm. Ammo will definitely be the biggest cost in the long run. I found even if I reloaded shooting 45 ACP was still expensive.
Rent or borrow a Smith and Wesson M&P, Glock, CZ Shadow, STI in 40 S&W and buy the one that fits your hand the best. Sig 226 is a good gun but the design really isn't suited for competition, similar to driving a jeep in a Formula One race you could have the best jeep in the world but it won't do that well on a F1 track.
If you're totally in love with the 1911 platform, which I can relate, the STI's in 40 S&W are sweet shooters. It will put you in Limited/Standard.
DavesNotHere