Isecond the idea of a good book. You have a lot of basic questions and would be well served by reading one of those excellent references.
1. how many lbs of liverock is optimal for a 55 gallon tank?
Depends. anywhere from 50-100 lbs, depending on the rock.
2. do i need powerheads? and which ones would be good?
You do need water movement. Powerheads are a cheap way of doing that. I would get 4 Maxijet 900s.
3. What are some good starter fish and cleaners to get me started once the water is stabilized?
Difficult question. Aggressive? Community? clowns, blennies, dwarf angels...all are good...not necessarily good together, though!
4. Optimal ph is 8.2? whats the lowest and highest safe range?
I say 8.0-8.4. Stability is key here.
5. and optimal specific gravity 1.020 to 1.022? Higher. 1.023-1.025
6. Is a protein skimmer absolutely necessary? I won't be able to buy one for 2 weeks .
I say yes. Makes things easier. Depends on bioload really and how diligent you are with maintenance.