How to create segmented reports by arbitrary custom variables or custom dimensions?

Suppose I have 100 clients and a thousand users of these clients who access my website. Is there a way to run custom segmented reports, based on say, clientID? If it is possible, what should I look into? custom variables or custom dimensions?

Hi,

Custom Variables and Custom Dimensions are nearly the same, but the latter are the more modern aproach and the one that is recommended to be used.

I did try custom dimensions and created a new segment. I am not sure how to create a report that group the data by the custom dimension, which in my case is Client ID. Is there a way to do it?