Ive been having great success with 1/3 perlite 1/3 rough Coco 1/3 compost or EWC.
The plants that hit this mix (once its amended) look great, and Ive even brought back a really locked out yellowing plant full force after transplanting into my water only mix.
(using this base)
I buy the 4 cuft perlite bag, 2.5(+) cuft piece coir coco in giant bricks and use my own compost/ewc when Ive got it. Otherwise local EWC or quality compost is easily sourced.
If you have a yard, look into free clean wood chips off craigslist. Throw these in a pile for a few years and the resulting humus at in the middle/bottom of the pile is a great addition to any soil mix, and its a CHEAP/FREE way to make very high quality, simple, clean humus from a local waste product!
Just research what type of wood your getting, and start cooking!...(hardwood is the best)
Cheapest soil building Ive done, and the best results.