Do you really think that I need to have test kits for phosphates, strontium, calcium, and carbonate hardness? Or can I just stick with ph, ammonia, nitrite, and nitrate?
Calcium/Alkalinity - yes, if you are doing SPS because you need to maintain calcium level for growth (and alkalinity to facilitate the calification process).
Stronium - not necessary at all - if you dose stronium as a separate additive - then just follow the directions. most people use a 2 part system and the 1st part contains calcium/stronium and other trace elements.
Phosphate - yes (imo) - but you can do this by having your LFS test it - i find the test kits not that good on this and you really need a meter for it. Phosphate facilitate algae growth so if you are haivng an algae problem - you need to know whether its phosphates.
If you are starting out - i would get a an ammonia badge (from Seachem) - they are fairly good. Once your tank is cycled and if you have a decent amount of LR - its doubtful ammonia and nitrite will be problems.
You just need to monitor ph/temp/salinity and keep an eye on nitrates.