That kind of price limit is tough. I would go to a store and buy new boots- spend like 100-150 bucks on ones that fit right. Then go on Craigslist in your area and find a board and bindings together for 100-150. Try to find something like this on CL K2 DarkStar 157 Men's Snowboard w/Boots & Bindings
Try to get the newest board/bindings possible- anything in the last 5 years. probably a board in the 154-158cm range. Take your boots with you when you check out the board to make sure they fit in the bindings.