heres my take on testing FWIW.....may save you some money if you buy into it
Any cheap tests for ammonia and nitrite are fine. The fact that they exist is enough of a result. These arent really even necessary IMO. Just let your tank cycle competely before you add anything....and if you are missing any LARGE fish you need to get them out........these should never be an issue
Any cheap tests inclucing the dip strips will work fine for nitrates. As your tank matures and your husbandry habits improve, this number will go go down or go away altogether on its own. Ballpark number is fine in the meantime.
Buy salifert calcium and dkh.........these are the important ones IMO. You can add magnesium to that if you start to keep lots of sps and/or clams
You can buy a salifert phosphate test kit, but it really doesnt read low enough, and the colorimeters that can are very expensive. If you can detect it with salifert, youve got a TON and most likely algae issues. you are better off buying a TDS meter to be able to ensure that your RO/DI is working properly and you are starting with pure water. Along with that skim well and dont overfeed and all will be well. Add cooking your rocks, and lifting it off the sandbed to this will also help your cause in the phosphate game.
Save your money on PH test kits. Buy a ph monitor and you wont ever need to test...you just keep it calibrated and you will always know what your ph is by simply looking. Otherwise i would suggest a salifert kit for ph, but this is another one that you will learn that isnt so necessary after a while. Keep your alkalinity in check and make sure you have good surface agitation and are providing the tank with fresh air so it can off gas the co2 and your ph will be in line.
All other trace elements will just get taken care of in your regular water changes and dont need tested for
jmo