Healthy, Inexpensive foods

Protein

• Eggs
• Lentils
• Beans
• Cheese
• Milk
• Plain Yogurt
• Canned Fish (tuna, sardines, etc)
• Frozen edamame
• Whole roast chicken (use the leftovers wisely, boil the carcass into broth to use in soups)
• Peanut butter (use sparingly)

Treat meat as a part of the meal, rather than the main attraction.
Grains

• Rice
• Pasta (I should buy the whole grain varieties, but am not so good about that)
• Oatmeal
• Popcorn kernels (I make my popcorn in a saucepan with a little olive oil, then just season it with salt)
• wild rice

I don't eat bread very often anyway (generally too lazy to put together a sandwich, and I'm not hugely fond of toast), so I usually make my own. Occasionally I'll make soft pretzels too. That takes about an hour of time (and my full attention isn't even needed for all of that), and I end up with enough pretzels to last about a week (just store them in a giant ziplock bag in my cupboard)
Veg

• Frozen veg (I like to snack on little bowlfuls of frozen peas, corn, and lima beans during the hot summer)
• Potatoes
• Dark Leafy Greens (good in herby stews, or just sauteed w/ garlic in a little olive oil and then seasoned w/ salt, pepper, and maybe turmeric. Add a can of black beans to that, and you have dinner)
• Cabbage
• Cauliflower (it's not boring if you season it well)
• Garlic
• Peppers
• Onions
• Broccoli (I need to find more things to do with this)
• Radishes (good to snack on)
• Carrots (not baby ones)
• Turnips, Beets, etc. (I need to get better about eating these)
• Canned tomatoes (make for a good base to soups and stews)
• Celery

Other vegetables are inexpensive too, when bought in season.

Fruit

• Oranges
• Apples
• Grapes
• Bananas

Those are the ones that are inexpensive all year round. You can get a lot more variety by buying things in season, and paying attention to sales. I snack on fresh fruit, and occasionally bake it into desserts. Frozen berries are great snacks in the summer.

Morning Oatmeal

Boil a kettle of water. Meanwhile, pour oatmeal in a bowl. Add a little butter, brown sugar, cinnamon, and a pinch of salt.
If there's time, start a pot of coffee, and maybe do some little cleaning projects around the kitchen (I always seem to have dishes).
When water boils, pour in just enough to cover oatmeal in bowl. Set a plate on top of the bowl to keep the steam from escaping. Wait about 2 minutes.
Maybe use that time to pour yourself a cup of coffee or slice up a piece of fruit to go with breakfast. Check on oatmeal. If water is absorbed, it's ready. Pour in a little milk if you're up for it.