the best soil mix for in door and out door is
60% potting soil (i recommend using organic makes the bud taste better)
15% perlite
10% building sand(make sure u get the one with out salt)
10% worm castings(great food for !DA Ganja !
5% pre-mix(get a N.P.K. of 12-6-6) (Be careful if u put more than one cup into the soil mix the pre mix will kill the plants root and youll have to start over again )