Soil test kits...pH only or N,P,K as well?

I was going to get a cheap soil pH meter, but I saw a complete kit that's only about $10 more. I like the meter because there's no reagents that will need to be replaced. Do I NEED the complete kit, or will the meter be enough for me? This is a small grow for personal use, nothing commercial about it. I'm trying to stay organic, if that matters at all.

It's always good to know levels of N P and K, as well as the PH throughout the life of the plant. It'll help u diagnose deficiancies should they occur among other things.