Gleaning is a great way to augment your food storage. This is a form of foraging but rather than concentrating on wild plants, you’re picking up corn left behind in farm fields, that sort of thing. Now, before engaging in gleaning, you MUST ask permission. Otherwise, you’re just stealing.
If you have farms in your area, talk to the owners. Quite often, there is a fair amount of good stuff left behind, such as at the corners of the fields or when they dump the pickings into trucks.
Check your local parks and see if there are any fruit trees there. If so, ask at the park and recreation department about picking up windfall apples and such.
You might have some luck too in talking to local gardeners about getting their trimmings and thinnings. With many plants, you can repot these and grow them.
If you have factories in the area that produce food products, you might find they have small stores inside where you can purchase at a discount “factory seconds.” These would be things like dented cans, mislabeled products, or other items that are perfectly edible but just didn’t get cut to the right length or something.
Some states will allow you to pick up roadkill deer, provided you buy the appropriate tags. This does vary state to state so check your local laws.
Remember to always ask permission before gleaning. It makes no sense to try and save money on food and then have to spend the savings on paying fines and such.