From the standpoint of economics, most of your testing is going to be with hobby-grade reagent-type kits. you don't need to worry about ORP for planted tanks, but TDS is useful, particularly when acclimating new fish.
My preferences:
NO3: Salifert (saltwater (Profi) version - good precision in the 5-20 ppm range and easy to use) and Sera (good for clear separation between 10 and 25 ppm)
PO4: Hanna low-range colorimeter (highest precision) or Salifert. Note: for both, above 3ppm, dilute 5:1 with RO or distilled water, then multiply result by 5. API kit is good above 3ppm
K: Salifert (good precision up to, at least, 50ppm), JBL is acceptable
GH/KH: Salifert (modified: use 5x the water, then divide results by 5) - API and Sera unreliable QC experiences
KH: Hanna colorimeter (used mainly at very low KH levels, such as <1 dKH and where higher precision for CO2 determination is desired) or Sera and API (modified: use 5x the water, then divide results by 5)
Ca: API (modified: 50 ml sample water, add 20 drops of reagent #1, each drop of reagent #2 = 2ppm)
Mg: easily derived from the formula: (GH ppm – 2.5 x Ca ppm) / 4.1
Iron: Nutrafin (may be labeled under the Fluval name)
Total ammonia: Salifert
pH: use a pen, such as; Apera PH20 or Hanna
Never use test strips.
This is a compendium of what the most testing that that might be done, you will have to decide how much you want to do but, if you say you are a "data nut", you probably won't be happy unless you can, at least, do all of these tests and, gradually, you will find which ones will be more or less useful to you.