I consider all flours to be decadent/celebratory foods due to the low-H2O/portion hazard but lack of seed toxins is definitely a plus. Blending them tends to mask their individual drawbacks:
Coconut flour is nice and low-cal so I always include it but the fiber absorption can get out of control so I limit it to 25% of the blend.
Almond, golden flax, hazelnut and other tree nuts/flower seeds have great flavor and texture but the calorie/polyunsaturate load adds up quickly so I also try not to use them alone.
Ground chia adds a nice spongy "chew" factor (I use white chia so it doesn't discolor the product), again around 25%.
Tapioca/potato/arrowroot starch are good if you want more carb/less fat with no flavor.
Chestnut/plantain/lucuma flours add carbs and a subtle sweet flavor, but are expensive.
Oat fiber comes up a lot as a GF baking boon but I haven't tried it yet. I'm generally unenthused about seed fibers so maize and amaranth wouldn't be my first choices either.
Lots of: urban hiking, cycling, sprinting
Lots of: fresh meat, seafood, eggs, organs, tubers, starch fruits, vegetables, meat fat, dairy fat, oil fruits
Some: cured meat, dairy protein, sweet fruits, rice, pulses, tree nuts, oil seeds
Minimal: soy, refined proteins, sugar, liquid carbohydrate, grains, refined oils, peanuts