How good does my system have to be to realize an improvement with cables?

Typically, the rule of thumb is ~10%

On the other hand typically your components need to be of a significant resolution and quality before you can really expect a big diffference. I guess, I would say $2,500 components. But, some folks do realize gains with less expensive components.

These rules can be broken. I remember when my average component cost was $5K. My dealer lent me a set of interconnects costing $2K each. I bought three pair! Completely worth it. I had recently upgraded and was very much aware of how much sound quality I would have gotten by buying components that were $2K more and these cables were a screaming deal. 
 

It really pays to try and not buy. Borrow from dealer, friends, lending library. The sound improvement needs to be worth it. Many times in budget systems it is hard to tell.

OP,

Yep, you got it. Hopefully you take the complexity as a challenge and enjoy getting the most out of your system through listening and learning. That is what drives most of us.

I am sure over my lifetime I have spent over a thousand hours, testing, evaluating and reading about different cables. They have made major contributions to the overall sound quality of all my systems. To calm down the harshness and high frequency tipped sound when my components were inexpensive and now to be incredibly transparent to bring through the full capability of my outstanding components.

Yeah, “it depends”.