I have everything from the most expensive media to pot scrubbers. IME pot scrubbers are just as good. The ones that cost a dollar for three, bright colors and look like a ball of little plastic springs.
You just need a lot of surface. And honestly, I think most of us have WAY more surface than the beneficial organisms need already in our tanks.
I would buy the cheapest rings or bio balls I could find. I would use them with pot scrubbers. The pot scrubbers alone do not slow the flow of water at all, and I do think some blockage of the flow is good. And I would use foam as well to further slow the water and remove particulates.