For a FOWLR, I'd say something like a DryTab master kit (containing Ammonia, nitrite, nitrate, and pH tests) would be the only "kit" you'd need. You'll need a hydrometer and thermometer, of course, but the alkalinity kit and to a lesser extent even the pH kit are not "must haves."
Now, If you start trying to keep corals, then maybe a pH probe, alkalinity test, and calcium test might be in order.
Nitrate tests invaribly work by first converting some of the nitrate to nitrite and then measuring the nitrire. So you can test whether you have nitrite using most nitrate tests - if the color is off the scale then there is nitrite (or you took your water sample from the local sewer by mistake). What you can't tell by this method is the concentration of nitrite. I personally think that a nitrite test is of marginal use for that reason i.e. it not how much nitrite that you have that interests you, it's only whether you have nitrite.