I will start with America's test kitchens flour mix. They tested many, many, different store bought flour mixtures. Their two favorites were Bob's Red Mill All purpose gluten free flour and King Arthur's all purpose gluten free flour. They weren't completely sold on either one but if you do buy a flour mix at the store ATK recommends buying one of these two. They decided to develop their own mix. They put their team together and tested hundreds of recipes using different ingredients finally arriving at the formula that worked the best for an all purpose gluten free flour
24 ounces (4 1/2 cups plus 1/3 cup) white rice flour
7 1/2 ounces (1 2/3 cups) brown rice flour
7 ounces (1 1/3 cup) potato starch
3 ounces (3/4 cup) tapioca starch
3/4 ounce (3 tablespoons) nonfat milk powder
Whisk all the ingredients together in a bowl and transfer to an airtight container and refrigerate for up to 3 months. America's Test Kitchen strongly recommends a scale to measure the flours...I did not do that but that is on my must have lists...a digital scale...
Americas test kitchen strongly recommends using Bob's red mills gluten free flours for your mix if at all possible. Most are readily available at grocery stores with out going to specialty health food or organic whole food markets. So first make your flour and next lets make bread!!!
Cheers to Happy !!