You should use the hashtags to get to those followers, let me give you some advice:
1- Using good hashtags: Use good hashtags for all of your posts, this will help other users to get to your content even if they don´t follow you, there are some interesting apps and tools that can help you choose good hashtags if you don´t know how.
2- Explore hashtags yourself and follow new people.
3- Post appealing and high quality content: Lets face it, if you just post photos taken with a 5 megapixel camera, no one will engage with your content. You need to use high quality content.