In a dooms-day scenario, you're best bet is to affiliate yourself with a local, ideologically coherent group whose identity is driven by a narrative of historical persecution and already practices pooling resources. In the event of government or institutional collapse, members of these groups would automatically switch to treating the group leaders as the main authority. And these leaders would be inclined get their community to take care of each other and pool resources.

Examples would be Jews in Israel and tribes of American natives. If you can assert membership in these groups, it would be a good investment to go through the process before hand.

If you don't have ethnic ties that are useful in that way, you could join a religious sect. The main example would be Mormons. They cluster in communities, have a persecution mentality, and encourage their members to store food and other emergency supplies. You'd have to at least pretend to believe their stuff though. I have trouble thinking of other examples. Perhaps Scientologists? Jahovah's Witnesses? I assume one doesn't just "join" the Amish. Mennonites?

If there are some survivalist groups that are already off-the-grid, that could be an option. Intentional communities, particularly of the survivalist strain, often care about ethnicity too though, particularly the ones in the US.

If you can't join a group, some countries might handle collapse better than others. One might invest in immigrating to a country that could tough out a collapse. Switzerland's canton-based political system seems pretty robust. Iceland has geothermal energy. The way the Japanese came together as a country during Fukushima was impressive (but you'd probably need to be ethnically Japanese to cash in on this). Rich folks seem to think New Zealand is a smart place to bug out.

New Zealand brings up another point. If a place, country or no, is a remote island has the ability to support itself without imports, it could also be a good option.