Freezer is your friend, as are the woods, feral fruit trees, and your parents' garden if they have one. Nothing quite spiffs up a boring old porridge or a bowl of cereal than blueberries and apples that you've picked yourself and surplus raspberries and rhubarbs from your parents.
Don't overlook trash -- stores throw out perfectly safe and edible by the motherload every day. Cold seasons are the safest because the food remains fresh for a longer period of time.
I pretty much overlook pasta, rice, potatoes, and bread altogether, although I do consume bread and potatoes if I happen to find some in the trash. But even then I choose to give the white bread to my fellow students while I only eat the dark bread (anywhere between 60-100% rye). My diet otherwise consists of meat, eggs, dairy products, vegetables, fruit, and grain in the form of a bowl of porridge in the morning.
I've tried to eat more fish, but I just don't like most fish that you can find at a palatable price.