As someone who started off on a dirt jump bike (custom dartmoor cody), just get a BMX. I initially got a BMX as a dick-around bike (because djs arent designed for pegs, even if theyre a chromoly frame, and suspension forks....nuff said). Eventually I got so used to the BMX that I built up a new one and sold my Cody build. I have a NS capital 26 rigid thats more of a cruiser bike, I got it for a really good deal, and my housemate mainly uses it these days. I guess Im kinda saving it to make into a race cruiser or something.
And geometry is way more important than weight. The Capital is 24 lbs (not intentionally, I guess I kinda lucked out a bit with it) and my BMX is 31 lbs. The BMX is waaaaaaayyyyyy easier to throw around. The cap may have the added stability of bigger wheels, but for the way I ride its pretty redundant.