Could you just buy wild yams from the supermarket and crush them up and put them in capsules to save $$? Or is the dried herb that you buy in the store the "right" one you should take? Thanks

It depends on whether the yams you see in supermarkets are genuinely yams. It's often the case that supermarkets sell sweet potatoes but refer to them as yams, so you need to verify exactly what you're getting.