Here's the ratio: 2 cups white rice flour 1/3 cup tapioca flour 2/3 cup potato starch flour (not plain potato flour)
You should up the leavening when using gluten free flours for baking. When using for just coating food for baking or such, or thickening, you can use plain rice flour. There are other combinations on the net that you can also use. It takes a while to get used to the substitutions, the texture and consistency of gluten free items is substantially different than wheat based items. I made Heather's Peppermint Fudge cake the other day GF and it came out great.