Any experienced guy in creating some testing instrument here ?

What'd the simplest, cheapest and most practical ESR meter circuit be, requiring only 6 V PS (not 9 as usually) while it's reliable enough to perform a test with ~ 2 % (or just 2.5%) tolerance

 

Why do you have a constraint on the supply voltage?

 

Any experienced guy in creating some testing instrument here ?

What'd the simplest, cheapest and most practical ESR meter circuit be, requiring only 6 V PS (not 9 as usually) while it's reliable enough to perform a test with ~ 2 % (or just 2.5%) tolerance

You do realize that your three requirements create a substantial conflict with one another. Simple and cheap might go together, but when you add practical, those two might not be achievable. Let's see what the community comes up with. Here is the result of a Google search. To me it does not appear to be either simple or cheap. I have no opinion on practical.

How to Build a ESR Meter Circuit (makingcircuits.com)