I wrecked my Zuk 300 (i forget what model, but a slow pile of crap) twice in the first few months, and I wasn't doing anything aggressive (although arguably stupid on one occation). The bike was a hand-me down, so it was no big deal, but the road rash wasn't fun.

If you look on craigslist, there are dozens of running bikes available for under $1000. I would just buy a crappy old bike and ride it until you're bored and feel you've really gotten a good handle on it.