Equal parts of mother earth (sandy loam) bagged compost (from manure) , and potting soil and sometimes tree trimmings thrown in. I dump everything in a pile, mix it and let it sit. Over several months it smells (and looks) like forest dirt. My potted plants seem to be happy with it, as does everything I plant into holes I amend with it.
My "bee habitat" plants (perennial flowers) which I planted in my ordinarily wasted space under the eaves of my house thrive with a good mulching on top.