I use the same suit and goggles in open water that I use in the pool. Use the same suit you race in in the pool to race in open water; unless it is a wet-suit legal race, then you might consider one.
The most important thing you need is open water training, not open water gear. Work on open water acclimation, sighting, navigation, pacing, endurance and race tactics. You can pick up a lot of these from other posts on the forum or I recommend Open Water Swimming, by Steve Munatones (available at most on-line book stores)