I too like prepping and would like to be able to forage on wild food. I tried oak nuts and, if properly prepared (boiled many times over) they ain't too bad and in the season you can have an almost unlimited source.
I tried dandelion and it's pretty good, although it requires some time to harvest enough. Berries too, although the wild variety is not very digestible (the blackberries around my house, for example).
Wild vegetables have phytochemical compounds (often of the polyphenols group) which can be pretty healthy, they tend to be more concentrated than the domestic varieties. The phenomenon of xenohormesis is pretty interesting and convincing.
https://en.wikipedia.org/wiki/XenohormesisThe best for sustenance is of ocurse to learn some basic gardening skills, growing the simplest vegetables to grow, in all seasons.