I was in the same boat as you when I was younger. Really wanted a sport bike but insurance was crazy. I bought a Suzuki GS500 1st and rode it for a few years. Didn't really make my insurance go down though. I had to wait till 25 when it drops then I bought a CBR 600. My advice is go get your full M asap and look at something without a "R" in the name. There are some nice bikes out now like that. Kawi -Z, Suzuki SV, Yamaha YZ etc. They will still go pretty good. We've all been there that ride when we were young, it sucks.
With no insurance, like ODot said, they will sue the shit outta you if you were in a accident. And you probably dont wanna get into the habit of running from the cops. Helicopters are pretty quick