It's much hard to gain followers on Google+..
But this things worked for me..
1.Do comment on related post.
2.Follow other profiles.
4.Join public groups related to topics.
5.Follow back to your followers.
6.Send Google+ invitations to your email contacts.
7.Mention influencers in your posts.
8.Search for hashtags relevant to your business and use hashtag in your post.
9.Create and share comprehensive circles.
10.Embed a Google+ badge on your website or blog.
These things are basic.. May it helps you