What to mix with Fox Farm soil?

I'm planning to buy fox farm ocean forest at my local nursery.
Some people suggest mixing pearlite with the soil 50/50 ratio.
What nutes should I get for it or is the soil by itself okay for growing my babies? I see people used fox farm grow big. What is a simple soil mixture as I am really low on cash right now?

get grow big for a nute
get a cheap bag of perlite and add as much as you feel is enough.
I just wing it when it comes to adding perlite, like adding and mixing and seeing if the perlite overpowers the soil.

Some say 1/3 some say 1/2