You shouldn't waste time on social media platforms that don't work for YOU. There no one way to promote. Where do you get the most engagement? (meaning clicks, comments, likes).
Focus on whatever platform works for you. Keep the rest up to date with new work, but don't put big effort in.
Also keep in mind that viewers are common, fans are rare, and buyers are even more elusive. It takes someone a few repeated exposures of your work to decide they're interested, then sometimes even more exposures to decide to buy. And out of 1000 viewers, maybe 10 will become fans, maybe. It's a long game, play it smart.