You dont "need" LR, but its a good thing to have in your system. If your afraid of the initial cost of it you can get "dead rock" with some rock rubble from a more established tank. This along with your LS will seed your rock and make it LR soon.
As for tank stocking if your just wanting to keep fish only: Firefish, *Fridmani Orchid Dottyback*, Cardinals, or asst. shrimps