A couple of years ago I dug about 30 bags of cheap potting mix into her
garden beds and they have never looked back. The heavy clay broke well into
the potting mix and the raised beds are looking great. Use about the same
amount of mix as clay and it has held really well with the garden blooming
well. The rain that used to run under her deck now stops and is soaked up by
the beds.

As a second bonus, once the heavy digging was done, everything turns easily
with a hand trowel, and potting seedlings etc. is so easy.
Hope this helps,
Peter