lol thats all well and good everyone has a play out on the street when they first start
wat nick ment was, will you want to ride vert ramps? dirt jumps? concrete bowls/parks? or street, like rails, gaps, manuals etc.
the type of bike you buy will want to be edging towards the disaplin that intrests you most. take my bike for example.
i ride vert and park so i have a fairly light bike but a bit more weight than normal so i have more stability in the air when riding vert. i also run my bars alot further forward than other people because im tall. things like that. the top tube length is up to your own personal liking really.
just find a nice bike to work things out on. you can add and subtract things you dont want to need as you want.
P.S. some good brands are Haro, Odayssay =S, Sunday, Verdae, Black eye and even giant.