stay away from buying followers and search for people in the same niche as you, quality is much better then quantity
When you give out quality knowledge on twitter, people will follow you, and tell their friends to follow you - its called be unique, and interacting with others.
Social Media Group. Join a group by send request on prclicks.me {at}gmail{d-o-t}com This is social media group which helps social media marketer to improve their sites visibility includes twitter follower, facebook likes, comments, testimonials and many more. There are many other techniques which is used by other social media marketing people, That social media person or experts will discuss your problems personally by sending emails. Join group to grow your business.
You can buy followers using Fiverr.com You can also try to interact more on twitter and try to start conversations and get involved in any hastag discussions - people following these will often follow you. The times I get the most new followers is when Im retweeting great content and getting involved in the community. Good luck!