Personally I use Facebook, Tumblr, Deviantart, Wysp, Twitter, and Instagram, but I'd say I focus most of my energy towards Facebook and IG right now. I don't spend a whole lot of energy on Tumblr because it's not the best place for posting original artwork, but if you do fanart you're likely to find a following.
Yeah, Deviantart isn't the bustling art site it used to be; I started there in 2003 and it was a great place to grow your following and actually get comments and feedback. Nowadays it's really hard to get noticed, especially if you're just starting out. That's why I'm trying out Wysp-- it's a newer art website with a decently active user base and it's easier to find good art. With DeviantArt, I feel the overall art quality has really gone down the crapper and it's garnered a bad reputation because of it.