Well the EI method can easily add just enough by watching the plants and reducing down one by one each nutrient of interest down a notch each 2-3 weeks and noting plant health, when a negative response is noted, add more from the previous dosing volume, bumop back up the last 2-3 week's amount.
After a few weeks, you have targeted the individual tank's need without a test kit.
For new folks I suggest pH(red sea narrow range kits, never use a wide range pH test kit!!!), of a pH pen(19-40$) or a pH meter if they are into things(70-95$).
A KH and GH test kit.
Most brands are fine for this.
You can double the mls in the sample from 5 to 10 mls, this gives you 2x more accuracy so you can measure 0.5 units of GH/KH.
I do not suggest other test kits such as PO4/NO3/Fe/K+.
If you must test these, get good test kits but this is quite optional.
Does not matter if it's a CO2 enriched tank or a non CO2 tank.
Actually non CO2 tanks do fine without any testing of any kind other than viewing the plants.