Incase of e-commerce ads, detailed look at the funnel metrics as Impressions -> Link clicks -> Landing page views -> No. of product views per session -> Cart additions -> Checkout -> Purchases. Analyzing drop rates at each stage will give valuable insights on how overall efficiency can be improved.
As you can find in the above funnel, your website plays a major role in each sales that you generate starting from increasing page views to final purchase. So, having a good website can actually increase your returns from Marketing spends drastically by multiple times and you will be able to scale your ecommerce business in quick time.
Having said that a good conversion rate is important, are you wondering what are the factors of an ecommerce website that affects conversion rate? Following are a set of few recommendations that will help you increase your website's conversion rate.