2 parts rice flour (I use 1 part each white rice flour and brown rice flour as a personal preference)
1 part tapioca starch
1 part potato starch (NOT flour)
The reason I use parts for my rice flour blend instead of exact measurements it that then you can easily make as much or as little of my rice flour blend as you want. For example: If you only wanted 2 cups of blend for a recipe then each part would be 1/2 cup. If you are like me and want to keep a huge canister in the pantry you can make a much larger batch.