If you shift focus away from wilderness survival, where materials are either scarce or require considerable amounts of processing to adapt, and toward making the best of a semi-urban disaster, where materials are plentiful but require re-purposing, you have a better shot at keeping costs down.

These are all hobo technology and common knowledge through the 40s but they have been lost as people got used to having to make their own gear. An example might be using discarded cardboard as a sleeping pad. Garbage bags as a poncho. A salvaged pillow case and light line as a functional backpack. How to stuff a cheap jacket with newspaper to make it a lot warmer.

IMO these skills are far more useful than many wilderness skills. Teaching them is easier also. In part because the materials are either discarded items or dead cheap. But also because you can teach these skills on a empty lot in the middle of a city. You don't need to carry kids out to the deep woods.