There's not an easy answer to this question but here's my two cents.. go to college or go to boot camp. depending on your families income you may need to get subsidized loans from salliemae or other financial institutions. depending on your grades in highschool or if you don't want to take the s.a.t's, start out at a community college and then transfer to a university after you get your associate's degree (2 years) get a work-study job on campus somewhere cool like a radio station, gym, or lounge area. the pay will be enough to get you by until you graduate. many people say that a college degree is like a high school diploma in this day and age so what does that make a highschool diploma actually value? a middle school diploma?
you could always learn a trade; be a mechanic or something by taking a 9-12 month certificate program. if your interested in sales work at the mall in retail at a store that has commission, or just go to college and study business so one day u can work with the big boys. If your parents aren't willing to help you out with a convertible they would probably rather put that money into an education. also you can try and be a rockstar or a rapper, and then maybe you can buy a few camaros