All purpose flour mix: make it first!

I call this my Proprietary All-Purpose Rice Flour Mix...now sharing it with the world! Usually I make enough to fill a large canister, because I use this flour blend anytime that a recipe calls for "all purpose" flour. (Note: if you CAN have gluten, you can always use all-purpose wheat flour instead of this rice flour mix.)

Mix approximately equal parts of:
Rice flour
Tapioca starch (also called tapioca flour)
Potato starch (also called potato starch flour, but NOT potato flour)
Then, for every cup of this flour mix, add 1 tsp xanthan gum. So, if you mixed 4 cups of each flour, you have 12 cups of mix, and you need 12 tsp of xanthan gum. Since 3 tsp = 1 Tbsp, you can use 4 Tbsp xanthan gum. Get it? Good! Now make sure to mix that xanthan gum in really well, because a little bit goes a long way. You don't want a little pocket of extra xanthan gum in your flour, believe me!

A few notes on cost...
If you have an Indian grocery store near you, great! Rice flour and tapioca starch are usually available there for a fraction of what they cost at a natural food store. No, they aren't labeled gluten-free, but I have a pretty strong gluten reaction, and I've never had any trouble. I get great prices on potato starch flour as well as tapioca starch and rice flour at the Super H Market, a Korean grocery store with locations around the country.
Xanthan gum is pricey...no good solutions to that yet. I've heard that guar gum costs less, but I haven't tried it out yet.