I gain followers by following all of the people who like and retweets the bounty campaigns that i'm doing you can also follow all the people who has a #FOLLOWBACK and also you can like and retweet the followhelp twitter page.
Yeah I advise you same strategy. I follow bounty hunters, airdroppers, blockchain addicts etc. By doing so you may also get more referrer for airdrops. If they followback thats good, if they do not follow back, just unfollow them. I never follow people who has more follower than he or she follows. To unfollow unfollowers you may use manageflitter. It is easy to use. Last but not least,I advise you talk to your twitter friends. I have now too many friends all over the world for the sake of bounties and airdrops. When I need help for crypo related issues they always help me.