Frankly, you're best bet would be to hire an electrician.

Is your meter on the pole (unusual, but done in some places)?
You'll need to run a new service or feeder to the shed, depending on how things are now. The requirements for service installation are highly dependent on where you are local. You will need a service disconnect and panel (may be the same thing) as well as a grounding system (ground rods typically) if you are going to install multiple circuits in the new structure.

"...would like as much power as possible because a lot of heavy heavy plug usage and lights will be using electricity and possibly eventually..."

Not the clearest of specs. Approximately how many marijuana plants will need lighting? Are you starting from seed or will you be using clones? Any hydroponics involved?

:-) :-)