Welcome to the boards!!!
If they are selling you "cycle" they aren't very helpful. That stuff is a crock of crap. LR and a $0.05 cocktail shrimp is all you need to cycle. There is a HUGE difference between fresh and salt water. You can add a fish to a freshwater tank the day you set it up. You have to wait 6 weeks with salt water. As for the LR, I would get Marshall Island if you can. It is the best IMO. The rule of thumb is 1-2 lbs per gallon but it all depends on what kind of rock you get. With MI, you can get 1 lb per gallon and be set. If you get Tonga or Figi, you will need more as the rock is more dense.
Also, make sure you get a nice skimmer as it will be your secondary means of filtration after live rock.