I've made a "supermarket" E-6 First Dev before with great results.
Originally Posted by Diapositivo
I used Sodium Carbonate, Sodium Bicarbonate, Sodium Hydroxide, Ascorbic Acid, Paracetamol, and Sodium Metabisulphite (which I used to make Sulphite, though its simpler to start with Sulphite, which is also easy to obtain, for the purpose, I wanted everything from the supermarket as much as possible), and sodium thiosulphate can be used from pool shops for the solvent instead of thiocyanate, but I had thiocyanate on hand and used that, though one could possibly use a little fixer too.
Though it requires testing and adjustment of course, I don't have starting points on me, since I just use Kodak First Dev usually, and just add additives to it, if I need to increase contrast and restrain for old base fogged E-6 film, and still pH range is still necessary for the nicest results.
ATC pH meters are not expensive these days. and 200g 0.01g scales are also inexpensive, and accurate enough for our purposes.