Being 13, you've got a loonng time. I wouldn't even say HT, I'd say get a rigid (Kona Scab bump bump) or a BMX bike and really hone your skills. Then get a FS or a HT.
Not to brag, but I started on a rigid bike and rode all sorts of trails, and did 3-4 ft drops. Now when I riding my HT, I can ride lines that my buddies hate, and I can plow through stuff that sends alot of other riders skidding into the trees. I currently building up a rigid SS to start riding on the trails so I can work on my skills some more.
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Booyah!!