Every so often someone calls into the Dirt Doctor program on Sunday mornings here in Dallas (Radio access online) and tells about an epiphany and how they transformed acreage that seemed exhausted or marginal to begin with. They seem to have farm implements handy (or neighbors with them) and will describe tilling in hay and compost and then adding soil amendments, broadcast at whatever rate per acre, and it's interesting how quickly they can turn around this property. Generally this is somewhere in the Texas prairie they're describing, but it could happen anywhere.
The thing Garrett has learned over the years is that it isn't just the fertilizer aspect you get in organic material breaking down, in the addition of sugars (he uses dry molasses or molasses mixed into a sprayer slurry of compost tea).
If you don't have farm equipment, perhaps you can rent or borrow a tiller and work on one area to start a garden, and work outward from there. Howard Garrett isn't the only one who does this, but all of his information is right there online and is free - I find the permaculture process developed in Australia very interesting, but there is rarely much about it online because it is the subject of very expensive and rather exclusive classes, and has a terrifically expensive text book to describe it. Several hundred dollars is out of the reach of most hobby gardeners. Get it through the library if you're interested and take a look, but there is interesting work to claim or reclaim land that is not robust enough to support a garden as it is now.
If all of that is too much, then think about starting very small and put in raised beds with imported soil, and over time, expand those and always integrate the native soil in with the import, to get the benefit of the existing microorganisms in the soil.