what's the practical way to get more follower on instagram?

Twenty minutes a day commenting properly on posts from accounts your ideal follower already follows. Not "great post" - an actual sentence with a point in it. People click through on a comment that says something. Dull, and it works.

Pick one format you can actually repeat every week and stay with it for a couple of months. Watch saves and shares rather than likes - that is what pushes a post past your own followers.