I've been flying my Rush 2.5 trainer kite since Christmas, and I'm loving it. I feel a lot closer to it since having to untie all the lines, untangle them, and tie them all back. However, I'm looking to get my next kite. I want to kitesurf, so I really want one with a bladder. I know the best thing is buy used, but I really don't know where to start. I'll buy some cheapy wakeboard or just fasten some straps to one of my surfboards, but I need and kite and a harness. I think I just figured out that the number before the m is how many meters squared the kite is in size.

any help?

I went out today in 15 mph gusty winds and can pretty much fly my kite one handed most of the time. The strongest wind I've taken it out in was around 30-40mph and I slid a little when flying through the power zone. It put my wife on her ass, but I definitely need something much bigger to drag myself through the water.

You are right the # is the size. Taking a lesson is worth every penny. If lessons are available take one and discuss your wishes with the instructor. Are there any locals you can talk to about what works ? The wind speeds and your size effect your choices.
Bow kites or hybrids are generally considered good kites to learn on with their huge depower and easy relaunch. They can instill a false feeling of safety for beginers , some say. I'm fond of the Ocean rodeo One kite ( made near here ) and Best Waroo ( I'm cheap ). Both would be good but there are tons of choices. The main reason for buying used at 1st is that you will be very hard on your 1st kite. Resale value on new inflatable kites is disturbing.
Don't waste time on a wakeboard but your surfboard would work fine. Twin tips are better for learning / turning. You can make a Plydoor for about $50 and they work well ? Straps would also help learning but you can go strapless on a surfboard. If you buy straps you could use them on both your surfboard and a home job.