When our house was built, the contractor stripped off all of the top soil and sold it (a common practice) leaving nothing but hard dirt, stones and clay for our yard. The grass barely grows but no garden could be made from it. So when we decided to build our garden, we consulted with several local topsoil dealers to see what would be the best mixture to be trucked in to help us build our garden. We decided on a mixture of black & brown top soil and compost. This was labeled as the best for vegetable gardens and I must say that we have had good luck with it over the years.
Maybe your plot of land has quality farm soil, but ours didn't, and we had to have about 15 yards of it trucked in. But there is a silver lining in all of this: we have no rocks or clay in the garden, only pure, clean soil.
To add air spaces and additional nutrients to the garden, we added several large bags of vermiculite, perlite and peat moss. We mix this in good with the soil and it creates a light, almost fluffy soil mixture, which the vegetable roots really like as they can easily bore right thru it. Our soil is not heavy, solid, compacted or chunky, but rather fine textured, easily broken by hand, being very diggable and workable. This makes it easy for us to plant by hand, to till the garden in spring, to turn it over in fall, etc.
In a way, the lack of good native soil on our property was probably a good thing, as we don't think we could have gotten the soil quality we have now. By having the very best soil, compost and peat moss delivered to our home, we began our garden with the best of ingredients. Growing good vegetables is difficult enough, but when you have poor soil, it becomes almost impossible.