Alicia,
Are you
composting? Any soil is good soil . . . if you add enough decomposing carbon/bio-mass. Most commercially available "top soil" is just regular old dirt that is dug up from anywhere, and then mixed with a high ratio of
compost. So step one is to accumulate as much
compost as you can. If you can get a bunch of biomass accumulated (leaves, grass clippings,
coffee grounds, a cover crop, etc.), build a massive compost pile -- something 5 feet tall. Turn it every 3 days until it's done. That'll give you enough compost or three 4 x 8 foot raised beds.
Once you've built your raised beds and situated them where you want them, dig down 15 inches or so. Throw the soil onto a tarp or a couple of pieces of plywood (which will make it easier when you go to re-fill your bed).. Lay a good 6 inches of wood/branches/rotting boards into the bottom of your trench. Basically, make your
garden beds a hugel bed. If your raised bed is taller than 6 inches, then put a corresponding amount of wood in the bottom of your hole. Thus, if the height of your raised bed will be 10 inches, put 10 inches of wood into the hole. On top of those branches/sticks/wood, I like to throw a couple of 5-gal. buckets of coffee grounds. Throwing some extra nitrogen into the bottom with the wood will aid in decomposition.
Mix the soil you took out of the hole with your finished compost. With the wood that you placed in the bottom of the hole, it should raise your soil up to fill your raised bed all the way up to the top. Back-fill the hole with your compost-amended soil. Hopefully, it'll raise the level of the soil in the bed all the way up to the top.
Is all this necessary? It will make a HUGE difference in the performance of your garden bed. It will significantly enhance the water-holding capacity of the soil and will increase the fertility of the soil for years as the wood breaks down.