One of the Fastest ways to get Instagram Followers is by Following your target audience. They will see you Followed them, check out your Profile, and Follow back if they're interested.
VivoGram's Auto Follower does all that for you. You can target by setting Hashtags your audience uses, Locations they go to, & Profiles they are Liking & Following, such as your Competition.
Use Auto Unfollow to clean up your Following list. Choose to Unfollow people who don't Follow back, and Unfollow all profiles or only profiles Followed by VivoGram. You can also set a Whitelist for profiles you don't want to Unfollow.