Unless you're swimming in warm water all the time, a full sleeve is probably best. Any of the major brand names (and even the non major names) have good entry level wetsuits. I have Orca, QRoo, and DeSoto suits (well, just the DeSoto Speedtube pants) and they're all good. What matters most is the fit.

There's no real need to have a separate wetsuit for training and racing. I have multiple ones because the Orca is sleeveless and the QRoo is fullsleeve.