I started my Twitter account by doing a lot of 'follow trains' where you ask people to follow if you follow them. This is a free way to boost your follower count from the start without having to buy them on 'gig' sites like Fiverr etc

Then once you've reached a number you like, just delete all those follow train tweets and start building an audience the right way.

Why do this? You gain credibility having at least 100 followers than having none. It's a sleazy tactic, but it works.