I'm an SEO, so I sell everything from digital strategies/consultation, technological platforms, optimized content , paid advertisement (YouTube, Google, High authority publications) , and Paid Social Media (Facebook,Twitter, and Pinterest), and B2B / CPG commerce..
To get started, read everything Neil Patel, Moz.com, and Jon Cooper put out...your degree does not matter if you can demonstrate the knowledge
TV and radio are phasing out, and the future of marketing is going digital..that's where big companies are spending big money
Ironically, I do have Certs (4), but it's for Google Analytics...you can get these types of Certs by registering an Adwords account with Google.