My husband was transferred last year, and I spent 8 months cooking for myself until I could sell our house and join him. Here are a few of the things that I learned about cooking for one:
Buy meats in the smallest possible quantity and repackage them into single serving sizes. Label them with the type of meat and the date purchased, then freeze them until needed. If you buy in bulk and repackage, you run the risk of the food getting freezer burn before you can use it up, so you haven't really saved any money.
See if a friend or a neighbor would be willing to go in with you and split the cost of perishable items like eggs, milk, etc. That way, you each get a half dozen eggs or half a gallon of milk which can be used up before they spoil.
You can buy some brands of bread in "half loaf" sizes now, which makes it easier to use before it molds. Some stores also sell eggs by the half dozen. And don't overlook individual serving sizes of things like tuna, cheese and crackers, etc.
If there is a farmer's market or organic food store near you, buy your produce there. The fruits and veggies are usually better quality, and you can purchase just the amount that you need.
If not, then buy things like small bags of salad mix, pre-sliced veggies, and small containers of already peeled and diced fruits from your local store. They're a bit more expensive, but you will be more apt to use them if you don't have to fuss with them, and they won't go to waste. For one person, they are as economical as buying a head of lettuce and only using half of it while the rest spoils.
Avoid things like frozen dinners, prepackaged hamburger helper meals, etc. Even the so-called "healthy" ones are high in salt, sugar, and fat. Ditto most canned veggies and fruits. Fresh is always the best way to go.
Buy a good "cooking for one or two" cookbook, so that you won't fall into the rut of grabbing a sandwich or eating junk food because you're too tired or uninspired to fix anything.
Cooking for one person can be a challenge, but it can also be a lot of fun, too. Enjoy being on your own and the chance to fix good, healthy meals for yourself!