I think the best are Instagram bots. These are convenient systems by which you can accumulate real followers. Your target audience. It saves your time.
If you would like a good name of an ig automation tool, feel free to msg memail and I'll provide you to the name one I use. It has a 3 day trial, so you can try before you buy.
You can choose any good promotional tool for your Instagram account. You'll gain more targeted followers, likes and comments. You can send auto DMs using some promotional tools and do scheduled posting. But anyway you have to work on your account and do high-quality and interesting posts.
There are plenty of good tools which provide automated promotion. You can easily find the one that suit your needs on your niche.
There are lots promotional tools for Instagram on the web. Your choise depends on the price and on the functions that you want to use. As the functions vary from one tool to another. You have to check it yourself in order to choose the best one for you.