Mushrooms and microgreens. These can be grown in very small spaces. Mushrooms provide calories, along with unique medicinal properties. Microgreens provide condensed nutrition. Both of these can be cultivated for profit in most living situations, and with a fairly low startup cost.

Bokashi composting. Fungal dominated compost from kitchen scraps, including bones, dairy, etc.. Must be hot composted before being introduced to the soil, but provides a substantial boost when the process is finished.

I think these are the most important things to know about when it comes to gardening. There's a lot more that's important too, but I consider these the basics. I think there are multiple links on the channel for each of the things I mentioned.

Let me know if you have any questions or feedback. I'm trying to make this channel as user-friendly as possible.