You really don't need to add much if your going organic. Take it easy with your N,P,K's at first because this mix already has some of that. It contains Sphagnum peat moss, coconut fiber, earthworm castings, pumice, dolomite lime, and an organic wetting agent. You will need a good boost of Nitrogen for your early veg stages because the worm castings used are the phosphorous castings, not the nitrogen castings.
Some 5-gallon Smart Pots filled up with this stuff and some extra pearlite, preferably the large chunks, will blow you away. The roots will receive so much fresh oxygen but keeping moist and dark deep inside the choir. This will also air-prune the roots and form a very fibrous root system with feeder roots extending all throughout the pot. If you grow coco give it a try. I hope they come out with compressed blocks soon.