First of all you will need the following items
A pot. This can be obtained from the general store
Depending on which level you are you will need. (Carrot. Mushroom. Watermelon) These can all be found at the drug dealer
You can buy a pot from the F4 menu, if it isnt a gang upgrade (not sure)
Can you buy Carrot. Mushroom. Watermelon from the dealer? Am i missing something here?