Marketing 101: The Best Social Media Platform For Authors is great starting out advice. The opening paragraph set the stage well:
"One of the questions I get most often from authors—both new and experienced—is, “Which social media platforms do I have to be on?” There are a lot of ways to answer this question but I want to start by addressing the question itself, which is often phrased in exactly this way. The answer is: you don’t have to be on any social media platforms that you don’t want to be on. Social media can help you connect with new readers, raise your discoverability, and sell books, but it can also be a drain on your time, attention, and ideas. Social media is not for everybody, and not every platform is for every writer. So the first thing to do is let go of the guilt and pressure you feel to be on every social media platform that exists, posting content in real time. Almost no authors can pull this off and it’s not worth losing your sanity to attempt it."
It's well-worth reading.
Illustrate and Write On,