That is a loaded question...
It depends on your set up.
Your style, synthetic addies? bottled cycle kits? organic? TLO?
Are you able to mix your soil recipes? as in TLO.
Do you make teas and spikes?
I like a standard Pro-mix. nothing fancy.
I do TLO... True Living Organics. its a recipe of a soil mix that when done right.
it basically requires no ph checking and not a lot of feeding. TLO feeds the soil not the plant.
promix, perlite, earthworm castings, compost, and a list of other ingredients. some recipes have a lot of items, some are made for smaller amount of items.
once the soil is living (inoculated with micro organisms) its ready. using only clean water. non tap (chloros) .
and well water (high ppm).
just add teas to feed soil and you get best quality smoke anywhere.
To get a better response for what is best for you, let us know your requirements, anything that will help the
peeps give you a best answer.
Search medium, TLO or organic medium, bag soil.
read a lot of peoples set up. they usually list what they use.
Best I can do for ya. good luck