I use Compost that I made from all of my grass clippings and leaves on my property. Add that to last years soil and its amazing stuff. Basically amending my already good soil.
I also highly recommend using Recharge. Look on Amazon and read the reviews.
My plants are monsters!
I just dump a couple shovels of fireplace ashes and a couple bags of Black Cow manure in each frame and work it in good then plant. I get great yields.