I had a conversation on the clearnet about this couple days ago, and I think the most important thing in a "everything is fucked and i have to start from scratch" situation is community. Knowing people is the most important thing, you can have as many resources as you want, food, shelter, power, protection equipment (guns), whatever, but if you don't have other people, you're going to be SOL eventually when you run out of stuff.
So I have to say I'm woefully underprepared for such an occasion. Almost everyone I know, I know online, and if I know someone IRL they're quite far away from where I live. :(