Hey,
Welcome to the board!
:joy: :joy:
I'm not sure if you're talking about the Master test kit that Hagen puts out since it has something like 8 or 10 different tests all included in the same kit.
Anyway, I prefer the dry tab type of tests over the liquid variety. As far as what to test for I would recommend these for starters: pH, NO2 (Nitrite), NH3 (Ammonia), NO3 (Nitrate). A little further down the road you will probably want Ca (calcium). If you have doubts about the water you're using for makeup water a PO4 (Phoshpate) test may be required.
FYI, some lfs's will do some of these tests for you if you are only planning on doing them once in a while or if you doubt your test results are right.
HTH,
Dan'l