Mixing saltwater is not really that hard, get a good salt (instant ocean or reef crystals i use the second one), a refractometer (you can get one online for $50), a power head, a 5 gallon bucket and a good dechlorinator (i use Prime) or a RO/DI unit. Let it mix for 24 hours then check the salinity. Reef Specific Gravity should be about 1.023. Add water if the salinity is too high, salt if it is too low (if you add salt, let it mix for 24 hours again).
Ajer