If you buy a car with bad credit, you’ll just be paying too much in interest. So if you don’t need the car, don’t buy it. Instead, you need a “secured” credit card — a regular Visa or MC that has a credit limit equal to a deposit you make in a bank. Some require as little as $500 to get this kind of card. Then you charge a little bit each month — and PAY IT OFF ON TIME AND IN FULL EVERY MONTH!
Your payments are reported to the credit bureau, and that’s how you start rebuilding your credit. Here’s a link to an article and a search for a secured credit card.