There is no 'best' soil and nutrient, only those which others feel are 'best'.
If MG (organic, right?) has been working for ya, why switch?
However if you do want to switch, and have access to Pro-Mix HP, go for it. It's on the expensive side, but well worth the money.

I use mostly solid organics, and teas I make myself from the solids. When the time comes, you can top dress with:
Blood meal (12-0-0) -- go lightly. A little bit too much, and you'll fry the plants.
Blood meal is entirely water insoluble, so no tea can be made. But once the microbes in the soil get hold of it, they will effect a wicked short term N release. Then it plateaus to a low level but steady release that lasts around 6 weeks.

Bat guano - my favorite, somewhat expensive, but very gentle. It is partially water soluble, so a tea can be made. High N guano for veg (~11-4-2), and high P guano for flower (~0-5-0). It also contains millions of beneficial microbes.

Alfalfa meal - very nutritious stuff (~6-3-2 + trace elements). Partially water soluble, tea can be made.

Compost/humus - really good stuff high in humic and fulvic acids as well as microbes necessary for soil health and enzymes necessary for nutrient uptake. Partially water soluble, tea can be made.

Bone meal - (~0-10-0) Mostly for root health because it breaks down so slowly, but if you add it early enough, it can be a flower booster as well. Also provide calcium and contributes toward pH adjustment (upward). Totally water insoluble.
AlCapuco Reviewed by AlCapuco on . What's the best soil/nutrient I can buy? Hi, I'm new here. I was wondering whatâ??s the best soil and nutrients I can buy and where to buy them. Iâ??ve been growing for two years now and always used miracle grow moisture control and it has worked fine but I heard a lot of negative things about it so I need someone else's input. Iâ??m really confused. Should I stick with the miracle grow? And if I do keep using it, what nutrients should I add after the first 3 months? I hope someone would answer this. Thanks in advance. Rating: 5