Hello! I don't know anything about twitter so I'll only speak about Instagram. I started working on my instagram about a year and a half ago and just reached 20,000 followers! Here are some of my tips:
In addition to the course, listen to the podcast about social media as well, I found them both helpful even though a lot of information was repeated.
In the beginning, it does help to try and post a few times a week, or daily if you can manage it. I would prioritize Thursday - Sunday if not daily (Thursday is randomly one of the best days to post). When you post more often Instagram will share your work more.
As others said, you don't have many images up yet, so you'll want at least 9 up there before people will really consider your account active enough to start following it. Your last 4 posts were consistent, but your first two posts are really different so that might also be confusing people who might be interested in following you.
Promote to your friends and family that you have an instagram! Share it on your facebook or what not, often the first 100 followers are people that you know.
New features will always be highly promoted by the algorithm, so if you can figure out how to do reels those are getting a boost right now because they are the newest feature.
But for me the thing that I felt like really made everything "cilck" was understanding that it means to make "valuable" content. You'll hear this recommended by every article or person that you hear talk about how to make a successful social media account. I didn't really understand what that meant as an artist - if my art is good enough is it therefore valuable? For myself, what I came to realize is that "valuable content" means creating "sharable" content. You will only get so far with your own reach, if your instagram is inpiring and people to share it with others your reach will increase exponentially. Comics do well because they make people laugh, or feel understood and they want to share that with others. Tutorials or tips do well because people find them helpful and want to share. An illustration if it causes an emotional impact can do the same.
You can also participate in challenges and DITYS because the person hosting might then share your work.
There are of course other ways but that's been my thought process when creating my media accounts.
Hope that helps! Good luck