How do YOU structure topic clusters?

When you go about creating your 'topic clusters' how do you structure your content around your commercial/buyer pages, i.e. how many buyer pages do you incorporate per cluster (do you have more than 1 per cluster)? Have you ever tried creating an entire buyer page structure, like if it were split by region? Do you usually start with the buyer page first and then branch out or the other way around? Curious how you guys go about this, thought process, etc.