This was an interesting thing to think about this afternoon while digging up peanuts. TN Red Valencia peanuts in this part of Appalachia. Sweet potatoes, black eyed peas, & okra also do exceptionally well here. Beans & squash generally do good too. Chard & turnips are some more almost foolproof things here. Pumpkins & melons are almost as easy & reliable.
Our cattle are the weak point. To close the loop we'd need to have a few less cattle & dedicate more space to raising hay for the winter. A better rotational grazing scheme would also need to be implemented. That's a work in progress. So, ignoring cattle since that is probably not feasible for most backyards ... HOA's tend to frown on cattle.
If it became urgent we could eat all the squirrel we wanted. Pretty sure I could catch 5 per day by baiting some live traps. I think rabbit tastes much better & makes better fur so I'd start raising some pastured rabbits. Plenty of meat that way. Our chickens give us daily protein with eggs. If we wanted to eat the birds I'd get a rooster or two. Our chickens free range most of their food & have their own garden but to truly close the loop during winter I'd need to raise more grains & seeds. Maybe raise some BSF. I could hunt this property for deer, turkey, & other small game but I have better hunting available elsewhere so the wild animals here are just friends. Adding a couple of milk & meat goats would be easy enough. They are fairly self sufficient. There is a nearby river with fish.
When I first started gardening about 25-30 years ago I realized it made good sense to eat what you grow & grow what you eat. That has generally been my focus with gardening. For the most part I save my own seeds & could do better if it was necessary. I make it a point to eat something grown here almost every day of the year. A greenhouse would provide more year round options. If I gave away less or raised slightly more & preserved more I could avoid grocery stores entirely. Wouldn't have everything desired but it would be tasty, filling, & nutritious. There are just some things we like that won't possibly grow here or are more work than it's really worth. So we shop for those things. My garden area for the past few years has been about an acre. Roughly 1/4 has seen continuing soil improvements from onsite & has been actively gardened. I'm slowly but surely expanding & improving it but it supplies about 50-75% of our food now. Without fossil fuels or other outside inputs. It takes some work & some learning & some practice but it's quite achievable. It could be ramped up to 99% without too much problem. This hugelbed
provides an amazing amount of food. Salt would be tough but fortunately it's cheap & easy to store. I could always hike to get some via this trail
but that would be off site. Several days walk offsite. It's more likely I would trade some honey for the salt. Honey is excellent barter material for almost anything one might need.
Buckwheat flour. It is very tasty. Chickens, bees, & people like it. Hard to complain about buckwheat. Easy to grow & good for building soil.
I consider vanilla beans their own food group. No idea how to solve that problem. The point being ... no one is an island. A little cooperation with friends & neighbors make the task easier for everyone involved. My suggestion is start small with high probability foods & work your way up from there. Some annuals, some perennials, & some nuts. Various fruits too. Don't forget asparagus. Once it's established it's good for many years. Get the soil right & the food will come. One day at a time. One step at a time.