The digital marketer usually focuses on a different key performance indicator (KPI) for each channel so they can properly measure the company's performance across each one. A digital marketer who's in charge of SEO, for example, measures their website's "organic traffic" -- of that traffic coming from website visitors who found a page of the business's website via a Google search.
On the other hand, marketers who employ digital inbound tactics use online content to attract their target customers onto their websites by providing assets that are helpful to them. One of the simplest yet most powerful inbound digital marketing assets is a blog, which allows your website to capitalize on the terms which your ideal customers are searching for.
As for what should your sandbox be, you have a few options. The easiest is to start a blog. That’s what this site was started as: a sandbox for learning content marketing, and it only became my full-time job on accident. A blog is a perfect sandbox for learning digital marketing since you can test almost all of the tactics on it, it’s low-cost, and you’ll improve your writing in the process.