Boardersbestbuy.com is a good place to watch for deals on wakeboard equipment. The size and the speed are going to be the two biggest factors in your first wakeboard (you're not going to be too worried about how much pop you're getting off the wake initially). I'm 6'2" 200lbs and I ride 142-144s. You can also read good reviews on the board at wakeworld.com .. Hope this helps and hope you have fun, it's really a great sport.
P.S. Landing one foot on and one foot off at 20mph really sucks on a wakeskate. I skateboarded for a long time, but find wakeboarding generally a bit safer (just my opinion)