White < Wheat < just about anything else.
Flours can be made from just about anything that can be made into a fine powder. When it comes to the ACD, the lower glycemic index and higher protein content of a flour, the better it is for you.
My most-used options include:
Teff - a fine flour, favor is green/earthy/nutty flavor. Mixes excellently with cinnamon.
Garbanzo Bean - a bit clumpy, needs salt; mixes well with millet
Brown Rice - very fine flour, a bit crumbly and dry on its own; no distinct flavor
Millet - slightly sweet, very versatile- especially in mixtures
Amaranth - very earthy, slightly nutty flavor; I recommend mixing it... or it's kinda gross.
Coconut - tastes like coconut! very dry, thus needs extra egg/liquid in recipes. heavier and clumpier.
Spelt - WARNING: has gluten in it, be careful! but a tastefully nutty flavor
Tapioca - white in color, ultrafine -- use in baking to enhance consistency and cohesion
Oat - nice neutral flavor; a bit heavier.
All Purpose GF Mix (Trader Joes / Bob's Red Mill) - there's something weird in all of these, and I think it might be sourghum flour. At any rate, I think they're gross unless mixed with lots of other flours, so be careful!
Almond flour - great taste, raw, but extremely expensive... thus I have not really used it.
Starches: use all of these to improve cohesiveness of baking doughs, or to thicken fillings.