You can add the compost to the clay you have, there is no need to buy something called "topsoil". Lay that compost on your clay soil, but without the landscape fabric, and in a while your clay soil will change and become a decent planting medium.

Agreed. Compost itself is not a great planting medium. You need soil with a light dusting of compost on top.

If you can't afford anything else, use what you have ,your roots will penetrate that compost easily and your Clay will absolutely love having all that Compost on it, besides, that Compost is going to shrink into and amend your clay soil so fast, it'll make your head spin.

Put it down, keep it moist and plant in it, you'll be fine.
No harm,no foul ;-)

In the pics, do notice the rapid shrinkage,even on the tarp,the process of composting takes place as long as there is moisture.

These beds are pure compost on top of Clay soil, I have harvested so much ,in so little time, even I am amazed ;-)

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Now , this "bed" is Pure compost on a tarp,no ground contact (it is my excess compost)

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