Wow you are doing well for a startup. You will love the tank you are getting especially with the metal halide.
1. Normally the standard is 1-1.5 lbs. of live rock per gallon of water. Use this as a base decision but remember that you want rock that is more porous. This is to facilitate the aerobic and anaerobic bacteria needed for your biological filtration. And because you want the porous rock it will be lighter and larger than the more heavier dense rock.
You will see many options for your rock. Uncured, cured, base. In short uncured comes to you the fastest directly from the ocean. It has all the life on it that it had in the ocean but some of this life has died in the shipping process. Because of this the rock will stink, when you put it in your tank it will take longer to cycle and your water will be dirtier. The good thing is that it will have much more life in it that you can have survive the cycle and get some interesting things.
Cured rock is the same thing but the fish store has done some of the dirty work for you. They keep it in bins in their store and they put up with the dieoff and everything that goes along with it. Your tank should cycle quicker with cured rock however you will not have the same diversity you would have with uncured rock. Cured rock is usually most expensive.
Base rock is dead rock with no life on it. It is naturally the least expensive.
Most people in an effort to save money will buy maybe up to half of their total rock as base then buy cured or uncured rock for the balance. Eventually the base rock will become alive and you will not be able to tell the difference between it and the live rock. Again you will not have quite the diversity as you would buying uncured rock totally.
2. The same standard applies to live sand. About 1 lb. per gallon of water. You can get live or just dry. Most just get dry and let the live rock seed it also.
When you get your tank post here again as you will have it in front of you and we can better help with the setup of the sump area.
A refractometer is a fine choice if you can fit it into your budget now. Also a thermometer, and the ammonia nitrite nitrate and ph tests.
There is no need to vacuum you sand. If you get the correct clean up crew they will do it for you. Also if you feed sparingly once you get your fish there should not be much that needs to be vacuumed. We can talk about this more later also.
For the most part you are going to get the tank, test kits, refractometer, salt mix, rock and sand. Put it all together and then you will be waiting for about 4 to 6 weeks before adding anything else. During that time you will be testing, reading, looking at the rock and seeing all kinds of strange and wonderful things pop up, reading, possibly doing a water change or two, oh yeah did I mention reading?
Good luck and welcome to the addiction.
