BMX - buying a bike

I am looking to buy a bike but I don't know what I want to spend. First of all I'm 25 about 165 and I don't know about comfort or whatever. I don't know what size to look for I see alot of 20" is that a good enough size ? Help me out.....

Are you look for BMX,MTB, or one of them sissy french bikes, if you're looking for BMX got with 20" cause most of them are 20" except a few dirt or race bikes wich are 24, and there are a few 16 inch bikes too. I have honestly no idea about MTB, or pansy lil french bikes, pick out what your most comfortable on thats all i can say, also here are the few bands to stay away from, ANYTHING AT WALMART, Mongooses under $300, and pretty much everything under $300. Thats all i can tell you.

my bike was less than $300 :(

i guess its not that good

pansy lil french bikes
hey dont knock on road bikes, ride a fixed gear and call it pansy.. Go on. And lil is a pretty pansyish word amd 27" wheels are not "lil" compared to 20".

I just call em that cause my gay uncle rides em. And cause their lil tire(width wise)

first of all how tall are you. that pretty much detrmines the top tube that your going to need. and try to stay away from all mogooses.

5'10"

Well, you definitely want something with at least a 20.5" top tube.

im 5' 10" too and i ride a 20.75"

Im 6'0 and rode on a lil 82 gt for a long time it has like a 17 inch top tube :-/