Back to the Newb (as apposed to Knob), I agree with what Joe says, smaller is often better with wetplate. By smaller I mean about half or whole plate. Keep in mind there is a lot of learning in this process, it's cheaper to shoot 50 half or quarter plates to learn your chemicals and lens, and then shoot some large ones. But if money is no object do any size you want. Keep in mind the aluminum or glass costs too, as do the chemicals, lenses, everything is more when you get above 8x10. If you want a halfplate petzval figure on $200. For a 11x14 petzval, figure on $500-$1500.

I've been shooting halfplate for two years, with inserts in my 5x7 and 8x10 cameras. For learning you may shoot at least once a week, 4-6 plates a session. If you have different size inserts for your wetplate back you have flexibility. When everything is going right, put in a large insert and shoot that 8x10! When you have an off day, save your chemicals by shooting small stuff.