Buying first car, no established credit, 3k saved?

I will soon be turning 21 and i just got my DL, been working and finally saved 3000 for a down payment on a good car. My question is would i still need a Co-signer? Would i be approved to get a car if i have no credit? Are dealerships better than private sellers? I do not want to buy an old car and put money into fixing it. So would the dealerships be a better bet? also i have heard car auctions are also good to go to if u pay cash? Im new to this and as you can tell i really need some good advice. If i do see a car i like an can afford, how do i go about getting insurance? thanks!