I think it depends on what you want to plant too. As stated before, making your own compost is a great way to add soil nutrients. If you can keep chickens their bedding and manure is excellent for gardens, plus you can let them run around in there when the veggies are picked and they will scratch up the ground, eat harmful insects, and fertilize the ground. A small flock can probably maintain themselves off of your food waste and they will provide you with eggs. A worm bin is really easy to set up and there is an excellent tutorial here
http://garden.org/ideas/view/d...
Typically anything you can do that is just gathering from around you or on your land is the best.
If you have a lot of downed trees or limbs you can also check out a hugel bed
http://garden.org/ideas/view/d...
