5 gallon or 3 gallon grow bag for my GCS Critical ...

Hey, 3 gallons of roots should suffice most indoor growing needs. I personally use 3 gallon for the few extra inches of height. Setup dependant, really, more roots more buds, in the end. Cheers,

If you want a larger plant, go with a 5-gallon, otherwise a 3-gallon is probably good up to 200-300gram yield, give or take. i'm a soilles guy, so i can't recommend much about soil. Somethign that isn't too "hot". You'll want to add perlite or vermiculite to whatever you but. Try to get to a 50/50 mix of soil and perlite or vermiculite+perlite etc. If the soil says 25%, you want to add 1/2 of that volume worth of vermiculite or perlite (3 parts each). get a well-balanced feed, and take it easy the first 4-8 weeks. the soil will have nutrients. you'll slowly ramp up your fertilization.