[loisba]

I notice a lot of recipes call for potato starch, which of course, I don't have. I'm very limited in what is available to me locally, and my limited resources prevent me from doing much buying online. My mom, bless her, sent me a couple of boxes filled with flours she had found in Akron, rice flour, soy flour, buckwheat flour, corn starch (of course, that I can get locally), corn meal and corn flour, arrowroot powder, and xanthan gum. From what I've been reading, I think I could substitue the arrowroot or the corn starch for the potato starch. (Correct me if I'm wrong, please! )
But my real question is, can I substitute instant mashed potatoes in any way for the potato starch? And I've also noticed references to potato flour. What is that? Can the instant mashed potatoes substitute for that?
Sorry for what I'm sure is a really dumb question, but you never know until you ask, right?