I have a large Instagram following (116k right now). For me it was that I happened to be doing the right thing at he right time. The way I approached men's hairstyling was backward to the rest of the barber/stylist scene and because it was actually how I operated and what I believed (not faked for followers) it caught a lot of attention. After the followers started growing I read a lot of marketing books to find out why (Seth godin is amazing). The following gave me some amazing opportunities I wouldn't have gotten otherwise, like traveling the world to teach how I style hair. It also got me into photography, I started noticing that some hair pictures got more attention than others, and the quality of the work had less to do with it than the composition of the picture or the expression on the client. Neck tattoos and beards will sell any haircut.
Anyways, all that said, I get a lot of questions on how to grow on Instagram and my first response is a question. What do you want to get from your following? Usually stylists and barbers tell me they want endorsements. I've gotten maybe $1,000 worth of hairstyling tools for free because of my following, but it took me 1000's of hours to build the following- if I was doing it for free brushes it would be the worst paying job on the planet. I do it because what I know works for me, it's built my clientele tremendously over the past decade, and I've seen many of the philosophies build clienteles for dozens of other stylists and barbers. It's like an itch to communicate something that I used to think was a universal truth but learned later was unique (basic idea is that hairstyling is less about product and more about techniques)- the rest of the industry is trying to sell products to solve hair problems and I'm trying to get technicians to act more like teachers.
I got side tracked. Sorry. What I'm getting at, is Instagram can do great things, but you get better clients the old fashioned way and you can buy gear by working 1/100 as long at your day job as you would by sitting and interacting on IG. Plus people can smell if you're trying to get followers vs trying to offer them something of value. A following is a side effect to sharing inspiration, education, or entertainment and it usually works better if you're not faking it. Or you could just steal content left and right and get a repost page with 500k followers. The goal with every post should be to evoke people to tag their friends.