Cooking for large groups is an important skill. You can scale this up from large batch/mealprep to small gatherings to large gatherings. I’ve seen several large gathering situations where it was extremely noticeable when there was just 1 person skilled with this, and also when there wasn’t.

Scrapping/dumpster diving. Works best if you have a decent amount of storage space and a cargo-suited vehicle. Tapping the waste stream yields bounties. All sorts of things can be fixed up or sold or even used as-is.

No one’s mentioned this yet, and I don’t relish it personally, but being good@car is extremely useful. Everybody has car trouble once in a while, and being able to fix it yourself can save you or your comrades up to thousands of dollars a year.