Just anything you can get from Craigslist. Don't buy cheap shit from walmart, those bikes are trash. And you need to find a frame that fits you, there are different kinds. Bike should fit you like a glove, or you are not going to enjoy it and it's going to be painful. Buy the bike you like. Try it first, see how it feels and how it fits you. Watch youtube videos about bicycle fitment. I hope ill see you on the streets one day. And learn how to fix everything yourself. Just get a bicycle and keep biking. I wish someone told me to buy a bicycle when I was 18.