What is the best combination of gluten free flours to bake light and fluffy muff...

I am on a diet that also excludes corn and egg whites

First, the good news: the right flours can indeed make a difference. The optimal one I have found for a light texture is corn starch. As you say that you can't have that one either, the second best is non-glutinous rice flour. Try to find a mix with a high proportion of it.

Flours you should avoid for light muffins include:

• dark flours, e.g. from teff or buckwheat
• whole grain flours
• large-particle-size flours
• nut flours

Sadly, the third one is not something you can find written on the packaging - so if you want to develop a mix on your own, you will have to buy flours from different producers and see which one is ground more finely, then stick to that provider.

Also, when developing a mix, you should try to have a high ratio of amylose to amylopectin - so use lower amounts of waxy/glutinous starches such as tapioca starch of potato starch.

From there on, there is no single "best mix" for lightness, different mixes will be optimal for different recipes. If you have an existing recipe in mind, you can optimize a mix for it through trial and error - and notice that you will also have to optimize other things like the choice and amount of binders, and tweak the recipe a bit. This is so complicated that dedicated gluten-free recipe designers usually go the other way - they settle on a mix they like, then engineer their recipes until they work well with that mix. If you want to dedicate your time to this process, looking at existing "preferred" mixes and some rounds of testing should let you settle on a mix you like.

If you don't want to spend the time needed to engineer your own combinations of recipes and mixes, you have two options:

1. Buy a commercial mix. Try to find mixes which are formulated especially for muffins and similar batters, this will be a bit better than trying an "all-around" mix. The resulting texture will never be optimal, but if it is good enough for you, it is the least work.
2. Stop baking random recipes, find authors who have engineered their recipes to be gluten-free, bake these recipes only and follow them to the letter (this is much more important in gluten-free baking than in standard baking, because you have almost no leeway).
3. Stop baking muffins, completely. Muffin recipes tend to produce a rather heavy texture when done with wheat flour, and when you make them even more stody by going gluten-free, there may not exist a gluten-free muffin that you enjoy. If you want something this size, orient yourself towards baking cupcakes, which give you many more options to achieve a light texture.