To gain followers, optimize your account. the best way to optimize your account is by following a Instagram marketing strategy.
Content calendar
Don't keep on posting content randomly. set up a calendar and try to maintain the calendar dates to post your content.
Schedule post in advance
Schedule your post in advance to avoid any last minute mess and informing your followers in advance about your post will make it more engaging.
Collaboration
Create collaboration post with other influencers to gain more followers, as their followers will get to know your page too.
Avoid fake followers
Avoid fake followers for your page, as they will ultimately decrease the reach of your page.
Promote your page
Promote your page in Instagram and on other platforms to make it more visible for followers.
Connect with your audience
Interact with your audience through QnA or plan meet ups with your followers to make them feel important and valued. Try to reply to their DMs or comments.
Post content that your followers want
Keep your content relevant for your followers. Your followers needs to connect with your post in order to enjoy your content.
Hashtags
Hashtags can help you gain good number of followers. Use hashtags relevant to your content to increase your followers.
Post trending content
Post content related to the recent trends to make your followers happy and engage towards your content.