What did you make a few times that came out ok? Injera?
In my village we only have one Indian grocer. I've never seen flours of mixed grains there. That would be interesting, though I would probably make my own mix so I could have a more exact recipe. I've seen atta for making chapatis, and besan of course.
I've experimented with making my own version of baking powder using equal parts by volume of powdered calcium carbonate and citric acid. By weight, using the CaCO3 and C6H8O7 I have, the 1-1 volume ratio comes close to the mass ratio needed for complete reaction of the two to produce carbon dioxide (about 3 to 4).
I made something that turned out very good--I made a kind of pancake using 1 c. besan, 1/2 t of my baking powder, 1/2 t salt, chopped Indian green chilis, chopped green onions, chopped parsley and cilantro, 1/2 c sunflower seeds, and about 1 c. water. I mixed these, let the batter sit 10 minutes, then cooked like regular pancakes, using sunflower oil in a non-stick 6" fry pan. After cooking them I spread a little masti chutney on top. Made me happy. I grew up in India with pakoras and and I thought these were just as good. Edit: sunflower seeds are not traditional in pakoras, and definitely not needed.