I have the same tank, and I used 20 lbs of live sand (probably getting another 10 lbs today) and 20-25 lbs of live rock. Dont use beach sand, you dont know what could be in there contaminant-wise - there's all kinds of nasty stuff on beach sand (gas & oil from boats, sunscreen, dog pee - you never know!!) Live sand isnt that expensive, and the tank is pretty small. I paid $20.00 for a 20 lb bag. Do it right the first time, its more expensive, but will save you money in the long run. I am new at this also, but have done alot of research. Good luck!
Oh yeah, I also used water that is from the store, already in another tank, and my params are perfect (so far). No dealing with mixing the salt, etc... if you can buy the water from a store, do that!!
-Melody