For soil fertility, I recommend using the corpse(s) of an oligarch or two to enrich the soil (Human Composting). Would likely have to use some sort of anaerobic (no oxygen) composting set up so the right bacteria can get to work. This way you help solve the crisis, in part, and get some high quality soil.

Buuut that's longer term stuff that will take a while to set up. There are still a bunch of veges you can plant; beets, swiss chard, arugala, lettuce, turnips, kale, spinach, probably a bunch of others. Go grab some of that stuff, dig out a plot in your yard (if no yard use pots) and stick 'em in there. Usually there's instructions on the packet on how to and how deep to place the seeds, how often to water them, etc. The same information is easily found in so many places online also. Don't worry about soil fertility this year. If you have enough space you could just dig another plot and use that one.

Best thing to do is to start small and learn how you want to do things. Planning out an entire self sustaining garden eco-system would be a lot, even for someone with a well-callused green thumb.

https://plantisima.com/things-to-plant-in-mid-summer-for-a-delicious-late-harvest/