[A little extra explaination. Your salt water will be off the charts on the TDS meter! Salt itself is a dissolved solid as well as all the other elements we need in our reef tanks (calcium, bicarbonate, magnesium, etc, etc, etc.) so not only can you no measure it with cheap equipment (aka TDS meter) it wouldn't tell you anything useful.
Refractometer for Salinity/Specific Gravity
Test kits for the other stuff mentioned above (Salifert is a good brand)]
