I currently ride a foes Zig-Zag (it's a slalom bike). I race the expert class in Dual Slalom...I actually beat Buddy Antunez last year at Big Bear, but I would recommend mountain biking or going out to the bmx track to brush up on your ballance, timing, and bike control. I sold my motorcycle a few years ago and started racing mountain bikes, when I finally got another dirt bike my skills were so much better only after a couple hours of riding the dirt bike. If you are into just playing around for little money, go for the BMX bike! $300 gets you a good bike to start with and track fee's are usually about $5...very cheap, and lot's of fun, they also have classes just like motocross (age groups and skill levels)! Mountain bike's are a lot more pricey. My bike is about $5,000, and most "entry-level" bikes start at about $1,000! I have a few pictures posted in my profile, check it out!
Good luck, and just have fun!