Need test kit recommendations

To figure out CO2 levels, you need to know your kH and pH. KH can be pretty static, I bought a test kit a couple of years back and it hasn't changed at all. Maybe getting the water tested at a LFS would be enough to get a base line.

For pH, I recommend an electronic tester. They are getting pretty cheap, and are much better than guessing a color. You need some 7.01 calibration solution to calibrate the probe, and perhaps keep it moist.

When using tap water, I don't see much value in a GH test, like kH, you could get it tested at a LFS, or look at your water report if you get one.

The premise behind EI is "no testing", but if you are curious or want to establish a base line, I'd recommend a NO3 and PO4 kit. Some tap waters have considerable amounts of either, so you could adjust dosing accordingly.

What would you recommend for an electronic tester that won't break the bank?

Are these actually better than standard liquid-based test kits that use titration?

Much better precision. Plus it is easier to read a number than compare colors. Plus you don't have to mess with potentially dangerous chemicals.

I am not in the market right now... so I don't want to recommend anything specific, maybe someone who has done some research can chime in. A good starting point would be DrsFostersmith.com or Marinedepot.com and just check out what they have and how much they are. Brands like Hanna, Milwaukee, Pinpoint, I am sure there are a few others. Once you found one that you like do some googling for good prices, maybe ebay, whatever you feel comfortable with.

They have electronic testers at pool and spa supply places too, but they are still kinda expensive.

Aquatic Eco-Systems has a good selection of electronic pH meters. They will price match also. pH Meters