soil for greenhouse bed, perennials

The soil in my greenhouse is a heavy clay subsoil. I want to grow various woody perennials in the greenhouse, including figs and other small trees. What would be the best growing medium to fill a permanent bed without breaking the bank?

I got free wood chips by calling the electric company.

and dug down 5 inches and rich soil.

Any horse farms or riding arenas around you where you could fill up a pickup truck full of free manure? Mixed with wood chips, forest litter, leaves it would make a great sub-layer under top soil.

My primary sources are my friends' goat bedding (aged), my chicken compost, and wood chips from a local arborist.  I have added wood chips atop my large section of clay, and more diverse plants are starting to grow on it.