Working with the metrics tree starts with defining the goal. The first thing to remember is that the goal of a business is to make money. This means that the metrics tree should have a target metric related to money as the target metric. In this case, the target metrics can include several different metrics, and all of them can be on the tree at the same time, but the main target metric can be only one, and the whole tree is built from it. 

Analysts are often confused between North Star Metric and target metric. The difference is very simple, NSM can be anything at a particular point in time, and the target metric is always about money. And I recommend choosing between Profit, Turnover or EBITDA. In my work, I use a combination of Profit and EBITDA.