Matt Todd wrote: just piling organic matter on top and letting time, worms, and microbes do the rest of the work. Lasagna gardening is a good concept for how to properly layer so things break down well (sheet composting is another way to describe this.) Use what you can get, grass clippings, leaves, manure, etc.
If you are really patient and on a budget, get ahold of a tree trimming company and ask for a load of wood chips. They're usually happy to have a place to dump them. Spread that real thick on your area and over time it will decompose, enriching the soil and attracting worms to slowly till it all together. Keep it moist and maybe even consider adding mushroom spawn to speed things up.
This plus giving us a hint about the size of the lot and whether it's in full sun or gets some shade will all help us make informed suggestions!
Tereza Okava wrote:all of these options are good, and a lot will depend on your climate, your soil, and what you plan to do with it. What does the dirt look like, what kind of rain do you get, etc?