3 pilars for the base of your website:
1.) Acquisition. Know at any given time where your visiters come from? From which source they come from and to which landing page they arrive on? And the bounce rate for each of those landing pages?
2.) Conversion. What is the conversion rate of your registration and/or checkout form? What is the behavior of visiters prior to purchase?
3.) Loyalty. How do you retain your visiters and convince them to purchase? How good is your CRM (Customer Relationship Management) strategy?