I currently have an instagram of 2000+ followers (i follow 64). i have found the best way of gaining followers is to find a 'famous' instagram account(10k+) with followers who you want to follow back, i wanted a base of mainly female followers so i used a male account to gain followers off as their base is all female, in order to actually gain the followers you need to follow the followers of the account in hope they follow back. in a weeks time unfollow all of your following to get the ratio back to how you want.

There are websites out there but the followers are ghosts and do not like posts etc meaning you'll have lots of followers but 8 likes on a photo.