How many plants really depends on way too many variables. Figure out what size pots the final product will be in and find out how many you can fit in there, that would be the maximum. For soil 1 gallon per month of like so 3 gallon buckets are standard. Also if your going to pack them in tightly like that, make sure it's a strain recommended for sea of green gardening which will mean it tends to grow straight up and not branchy.