If we open up google analytics of Facebook ads manager - we will be immersed in a sea of data points and sometimes when we take a tip, we get lost and coming back to look at the bigger sky becomes difficult.
In my personal experience being deep into too many metrics made me myopic to the overall business health.
To avoid getting lost in the sea we need to hold on to a few key metrics that keep the big picture clear.
Customer Acquisition Cost or CAC as we call on a daily basis, this is no doubt the most important metric and the majority of the effort goes into improving and decreasing it day by day. (Total Amount Spent/ Total New Customers Acquired)
AOV - Average Order Value, if it is less than the CAC there is a big problem. Always make sure that AOV is way below CAC unless it is a high repeat category with a high lifetime value per customer.