Hi there, I have a tiny experience that I can share from my new vanilla PPC campaign management job, and it can relate to many walks of e-commerce, or online marketing.
I usually ask myself what is considered a conversion on my website, and how much is its value. For example a sale of a trinket is a conversion that can be measured in a sale, however signing up for a news letter is another, and so forth.
In addition, I would take each channel and product and setup a Key Performance Indicator. For example I had an e-commerce clothing customer that I walked through how to set attainable goals. We realized that an SEO project is long and expensive, and that generating direct sales from clicks on links may not be cost effective. Instead we made a strategy to promote her existing content to new look alike crowds on Instagram. That resulted in more people looking for her store on Google, after being exposed on IG. She's not growing exponentially, but her IG account is no longer marketing to get likes from friends, family, or people who already bought her products online. She's growing slowly but steadily with paid social media campaigns.
I consider myself a Junior marketer, so feel free to take everything I share with a grain of salt