While you can try testing yourself, a more reliable method is to contact your local utility and request the test results--it's public information, and may even be available on their webpage. This will give you a better idea of what is in your water, and without forcing you to buy a load of test kits you'll seldom use. Once you have this information, you can decide a) what water treatments are needed to deal with chorine/choramines. b) If phosphates and silicate levels will necessitate using filtered water (either purchasing filtered water, or buying an RO filter unit for yourself). c) gives you a base value to compare your salt mix to. Most slat mixes contain buffers and such to raise pH, calcium, alkalinity ect in addition to creating the salinity. Sometimes, addition treatments will be needed, especially if you want a reef (where calcium levels can be very important). So, I would get the stats from your utility, see what treatments are needed, and then mix up the SW and test again.
If you are on a well, you can still get the water analysis--think it's through the county. This will take one step out--well water usually isn't treated with chlorine/chloramines, but you may have a water softener, which may use phosphates for softening, in which case you'll want to get water before it hits the softener.
LR rubble means little chuinks of rock, 3-4 in a handful. Many LFS will sell these small peices cheaply--something like $5 for 10 pieces. They aren't as decorative as the larger pieces, but they will have the bacteria you want to kick start the cycling process.
Sand is great--preferred by most. A good 4-6 inches of it qualifies as a deep sand bed (DSB), which will allows the bacteria that break down nitrates to help keep your water quality up. I don't think you have enough for this depth--think that's probably only 2-3 inches deep. You can pick up more cheaply at a big box store (Home Depot, Lowe's)--look for a fine grained play sand, or blasting sand. Think it's usually around $4-5 per 100 lb bag.
Before long, you'll be helping others who are just starting out. 
