If you used potato starch and it was not smooth, is it possible you had potato flour instead?

Thank you both. My cheesecake recipe called for potato starch which turned out fine but not as smooth as I would have liked.

It's hard to answer without knowing the dish. But lastnightsdinner's answers are on target, with cornstarch being the cheapest and most easiest to find. Arrowroot will give a nice gloss to sauces but I don't use it for much beyond that.

Cornstarch, tapioca, or arrowroot are most commonly recommended to give you the same effect as potato starch.