Do you want to keep any corals in the tank, or keep it a fish-only tank? If you want a reef, I would suggest anywhere from 75 to 100 pounds of live rock. If you want just a fish-only tank, then the amount of LR is up to you...in a FOWLR, LR serves a slightly different purpose than a reef. Reefs need it for biological filtration wheras FOWLRs use it to supplement other filtration methods.
I wouldn't add fish until after you have all the LR that you plan to keep in the tank, because adding more might cause the water parameters to slightly go off track and hurt any fish in the tank.
Be sure to cycle the tank properly before adding any fish or inverts to the tank, as was suggested before. Good luck, and keep asking questions!