No offense, but as soon as I saw the words "DeviantArt" and "Tumblr" in your post, I face palmed.
To be clear, I don't say that to be ugly, but not counting all the drama that hovers around both sites, from both what I've seen and in my personal experience of using both sites as a way to host my art, DeviantArt is the MySpace of art sharing sites and Tumblr is only really useful if you draw fanart for a particular fandom (and not even then in most cases).On the subject of DA, Back in the 2000's when it was pretty much the only way to share your art, DeviantArt was actually pretty solid for the most part, but with the advent of social media sites like Instagram, Twitter, and I suppose Tumblr as well (though again, its not much better imho) in the New 10's, there really isn't a reason anymore to use a site like DA when you have far superior options at your disposal.
To give an example, back when I naively posted my art on DeviantArt, I barely got any attention. Like at all. (cue Tumbleweed gif) Not to mention DA is notorious for its bad user unfriendly site design. Posting just one of your drawings is like pimping out your high school English essay making sure to properly cite every last reference you used to write it! And even if you don't mind it, I've heard horror stories about people getting nasty viruses from DA because staff can't be bothered to check what kind of ads they run on their crappy site.
On Instagram where I'm at with over 300 followers, I get about 20-30 likes depending on what it is I post as I post non-art things too on my Instagram account. Not to mention posting your latest drawing or what have you is as easy as one two three and yes, that includes the (in)famous hashtags. My advice is to post three times a day, use about 6 hashtags at most per post, and follow people related to your niche of course. Before you know it, you should be able to build up a solid following. Source: Somebody who went from low double digits to over 300 unique followers over the course of last summer.
tl;dr Instagram is the way to promote yourself as an artist in my opinion.
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