How could I get a Sport Bike?

I'm 14, almost 15(will turn 15 on December 2nd) and I really wanna get a sport bike. I know I'm not at age yet but I have 1 year to go. I ride an old Honda Trail CT90 in the mountains on and off road. I know on the road it's illegal but I love it. I wear a helmet, but was recently caught because the sherrif saw the tags were from 1996 and he caught me without a license. Didn't get a ticket. But anyways I really want a sport bike. I have $100 saved and I'm trying to sell and old 1970s Honda Z50R. So with money from that and $100 after I sell it I may have $600-$900. I want a sport bike but I know with that money it won't be much. I can ride my dads Honda 90 to school when at age and continue to save, or, spend the money when I'm 16 on a cruiser(such as old Honda cb). Should I get that at 16 or continue to save? I'm in California. How else could I go about affording a sport bike? I already have a full face DOT helmet. Please answer.

Under $1,000 it's not a sports-bike, it's a black-hole with an appetite for money.
Keep saving.
Spend a bit on the mandatory safety course in the process, that will save you money for sure but may save your life in the long run.