Try to find plain potting soil with no nutes..peace
You can pick up perilite and vermiculite in 2-3 cu foot bags cheap at lowes or OSH. I buy whatever base soil is on sale then add my own mix. Fox farms is good if you want to take no chances and got $$$.
It is like $15 for a big bag of ocean forest, that isn't that expensive especially considering how much better it is compared to other cheaper soils
I pay $22 for Ocean Forest or Happy Frog at my local Hydro store. WELL worth the extra $$$. BUT, despite what some will say here, there is absolutely NOTHING wrong with Miracle Gro time-release soil. You just have to be careful when adding nutes for the first 8 weeks.