For salinity, I highly highly recommend the Hannah salinity checker. As for No3, Po4, Ca, Mg, and ALK, you could either buy salifert/red sea kits, salifert being the cheaper one but still as good, or you could buy the hannah testers for these as well. You dont have to buy all of them at once, you can go slowly. Salinity, no3, po4, and alk should be your priority now.