While I do believe Compost is a good thing, it isnt necessary for a successful grow.
Im using Gaia Green 5-5-5- x 2-8-6, and Azomite. x Promix BX. And in reality, Azomite probably isnt mandatory either. Its just good for the medium, and has a track record of improving minerally depleted soil. Which Probi HP-BX, have only small amounts of Mg/Calcium. I like the BX, as it holds water better, and I grow under 1000w HID. Its-Promix BX- still light though.
There is a whole section on this forum on how to use Gaia Green, and it is all but foolproof. This is my first time using it, and the feed schedule, and it couldnt be any more simple.
Only thing I noticed, and Im not sure if strain related, but, after about 3 weeks flowering, my plants ( Ace KA5Hz-Destroyer ) developed a huge Magnesium Appetite, so I upped the amount of Epsom Salts I add to the water, and they recovered. Previously I added ZERO.
Im sold on Gaia Green. It couldnt be any more simple. Just follow instructions, and keep watch on Mg levels. Especially in Flowering.