I don't know at what level you are currently, but I personally feel the harsh truth of putting your art online, is that it's extremely hard to stand out due to the baffling amount of art, both digital and traditional, that can be found online.
The things is that with programs like Fire Alpaca and Gimp being the free equivalents of Photoshop and every cellphone being able to take relatively good pictures these days, it's very easy for anyone to put their stuff up for all the world to see.
I think that is great, but it also comes with the inevitable downside that there's going to be a LOT of art circling around the web. And in turn, that will make difficult to be noticed.
Another result of that is that artist that still have a long way to go get less attention, due to the fact that even the best artists produce so much all together that even many of them get overlooked.
So, those accounts that feature art really have a luxury problem. They probably get a lot of requests and can't post everything. On top of that; if they only post the good stuff, the account will also get a lot more attention.
I'd say; keep improving. I feel that's the best way to get noticed. And also keep promoting yourself. Not just on instagram, perhaps. Sites as this one are great for getting useful feedback. Putting your work on something like DeviantArt or ArtStation (though the latter is more focussed on the gaming industry, though not entirely) can also help you create a followerbase. Tumblr is also an option, there are a lot of artblogs there that range from realistic traditional things, to 3D modeling stuff; anything goes.
Just keep going, basically. Standing out is tough, but persistance is how you get there.