What’s the bare minimum you need to navigate across land? For most people, that would be a compass and map. A basic road map is sufficient to get a rough approximation of the lay of the land. More detailed relief maps can help plan for elevation and estimate possible water sources but they also take up more room in your pack. Waterproofed or laminated maps are also extremely helpful. Lensatic compasses are the most reliable for little money. If possible, a compass and protractor are also extremely helpful for route planning. Obviously, not as essential but nonetheless useful.
A quantity of gold or silver may be a contentious inclusion for some people, but like cash, things will have to be dire indeed before both lose their appeal to humanity. A handful of gold or silver can be converted into just about anything of equivalent value, anywhere, in a hurry and gold especially can secure you a favor that you otherwise may not be able to get.
After 9/11, my dad filled a duffel bag with some energy bars, a couple gallons of water, some penicillin, and a map. Amid scaremongering headlines about imminent anthrax and “dirty bomb” attacks in the city, he wanted to have some supplies on hand in case we needed to get out of Brooklyn fast. Were he to assemble such a bag today, he’d likely stumble on a number of companies promising a more wholesale brand of disaster preparedness: a box full of shelf-stable freeze-dried meals, to be revived from their dessicated state with the addition of boiled water.