I don't use Instagram as much as I probably should and I definitely agree that getting a following on there can be quite hard. I got extremely lucky when I first created my account, got a huge boost that made me go from 0 to 182 followers in the span of a few weeks... then then it basically stopped there and it took me over two years to get to the 305 followers I currently have 
Overall, the things that seem to work for me are:
-
Make sure to post things at the right time. Seriously, that alone can make a HUGE difference on the amount of engagement you get. This applies to both posts and reels. From my own time zone (GMT+1) I noticed that stuff posted in the afternoon (5PM or 6PM) basically gets half the engagement compared to posts shared at around 12PM. So I basically just don't bother posting stuff in the afternoon.
-
Interact, interact, interact. Instagram REALLY likes it when you interact with other people, ESPECIALLY if they're accounts you do not follow. One of the things that gave me a huge boost as I was getting started was just looking for recent posts in art tags and liking every single post that vaguely interested me.
-
Use as many tags as you can, not just art-related tags, but also stuff related to the actual content of your image. Personally, I noticed that my posts that use solely "comic" and "webcomic" themed tags would do much worse compared to posts tagged with "alternative style", "long haired men" and "alternative fashion" + more generic tags like "artistsoninstagram" and "instaart". For some reason, the "tapascommunity" tag doesn't seem to work very well for me either: most of my reels tagged as such wouldn't even reach 100 views, except for one (1) video which got 4k views and another one which got around 1.5k. If you consider that my recent reels that do NOT use the "tapascommunity" hastag get from 3k to 12k views, you can easily see why I prefer to avoid the tag XD (speaking of which... dear Tapas, wouldn't it be a good idea to look into that? Could it be that the tag is being shadowbanned somehow?)
-
Reels: keep them short. The longer the video, the lower your chances that Instagram will show it to people. For me, videos that were shorter than 20 seconds were what worked best.
Edit: ...and OF COURSE, just as I wrote this post, not one, but TWO of my reels miserably failed on the platform 
speaking of which: one quick way to see if a reel was successful or not (at least for me so far, I'd love to be proven wrong on this one) is to take a look at your notifications. If you get nothing for the first 20 minutes or so and then, all of a sudden, you get a bunch of likes from people who do NOT follow you, it means that Instagram decided to show your reel to a bunch of random people, which increases your chances of going viral. If, on the other hand, you get pretty much instant notifications of likes coming from your followers... it's very likely that your reel is not going to circulate at all and will only be seen by your followers. No idea why it does that and what criteria one is supposed to follow to get the video shown to random Instagram users (my last two reels both followed the criteria I thought would work), but so far... likes coming from strangers = video is being shown around; likes from followers = video is stuck on your profile page and won't go viral.
