The 4 most essential metrics to track as you make any improvement to your business: Average order value, Customer lifetime value, Conversion rate and Net profit margin.
How to manually calculate profit and where you could gather all the cost data. Everything considered: COGS, shipping, ad spend, transaction fee, etc.
You can make a million but still be in debt. Too much focus on revenue while being unaware of your true profit can be dangerous for your eCommerce business.