Adapting from MFK Fisher's 'How to cook a wolf', here is her suggestion for food which will contain adequate vitamins and minerals, while costing as little as possible, both in ingredients and in energy. The book was written in 1942, during the 2nd World War.
Assumptions : you have access to a medium sized cookpot (say, 8" diameter), a chopping knife and board, a stove top for cooking (alternatively, nowadays, use a microwave oven and a glass or plastic bowl), and somewhere to keep the cooked food cool.
Ingredients
6 carrots
2 onions
1 head of celery
1 small head of cabbage
at least 8 oz of coarsely ground whole grain cereal (steel cut oats would be a good choice .. don't use a breakfast cereal containing sugar)
Additions depending on what is least expensive (which may depend on the time of year)
Tomatoes
Squashes - zuchini, etc
Kale
Beans
Lentils
Optional - between 4 and 8 oz of ground beef - for flavor and fat content
Method
Chop all the vegetables into bite sized pieces and put in the cooking utensil. Add the ground beef. Cover with water, bring to the boil, and simmer for at least an hour. Add the cereal, cook for at least another 2 hours. Let it cool, and keep in a cool place.
This can be eaten cold, though it will taste better if reheated, and with some additional seasoning - salt and pepper, or soy sauce.
"It is obvious to even the most optimistic that this sludge is strictly for hunger. It is functional, really - a streamlined answer to the pressing problem of how to exist in the best possible way for the least amount of money"