It's a big old beast.
Most folks are more inclined to use something like a Hach 890, or their 2800 spect.
Hanna makes a simple colorimeter, the C200.
These are generally much easier to use.
They also sell reagents pre made, however, you can buy bulk reagents and do your own test following water methods outlines etc.
I like buying the pre made stuff, and a simpler colorimeter is a bit more $$, but a lot simpler.
If you plan on doing a lot of test, then the cheaper routes are best.
But once a week etc, no.
Lamott's chemical(no spect or colorimeter etc) test kits are quite good for NO3, PO4 I like the Hach.
I use a thermo orion Accu IV, a Hach 890 and Beckman spect. I want to get the Hach 2800. I use a Hanna colorimeter for the K+.
Hanna ISE pH/Thermo, calomel Redox reference meter, a Milwuakee O2 water and polargraphic probe for O2 on a YSI(no membrane issues).
For CO2, I made a special O2 membrane for the pH probe and use the KH reference solution inside the pH probe and take the readings based on the ref KH and the pH.
Overall, this can tell me a lot.
BTW, lighting is easy to measure if you use a PAR metter, Apogee is the best deal there is bar none.
299$ for a PAr light meter that's got a nice water proof probe.
Better than the 1000-1500$ LiCOR.
So there's chemicals, gases, light.
I have scales, flask, and other items as well.