I have to start buying groceries, what is normaly on a grocerie list? please help!!?

Im 21 and I live with a friend of mine. we eat out literaly every single meal and it costs me about $100 bucks a week. I need to save money and eat better. Im a fireman so I need some quick and easy to make meals for the fire house also. All I know to buy is sandwich stuff and that gets old fast! I can cook farely well I just dont know what to buy to cook meals. any help??