Salmon comes in foil packages that are easy to store for a long time, as well as flour, sugar, yeast, salt, pepper, spices and flavorings. Canned goods, etc. Milk in the cubes. Water comes this way, too, a good way to stash an emergency supply.
I don't have any suitable land for gardening, but plant occasional crops like carrots, radishes, lettuce, etc. in large containers.
Knowing several low-tech skills is a big plus. Soapmaking, spinning/knitting/sewing by hand, pickling and brining, etc.
Anybody can do this much. Do it a little at a time, and before you know it, you'll have a nice supply of goods for keeping or bartering. Oh, yes. Make sure to get plenty of Baker's Chocolate and cocoa powder.
On Doomsday Preppers I saw the one lady preserving eggs by coating them in some kind of cooking oil. Does this work?
I cringe watching that show. The same lady was training other women on self defense but was obviously very out of shape. She was also giving firearm classes where they were shooting at small targets laid on the ground.
Yes, that last much longer than candy bars. I'm also thinking canned choc syrup.