I'm no expert (first tri coming up in 2 weeks) but based on what I've read, I think I'd wear a quick dry sports bra and some tri shorts under my wetsuit, then add a jersey for the bike and run. Or you could wear a one-piece tri suit under your wetsuit. (Be forewarned, though, it's a pain in the butt to go to the bathroom in a one piece tri suit. I'm learning that the hard way as I'm practicing in my tri suit.)

I don't know what to look for in a wetsuit for triathlons, but I've ordered one online for diving and it worked out just fine.

Good luck to you!