I have a couple of ideas let your friends on other social media sites know about it.Such as Facebook, Twitter and Linkedin. In this case Facebook is probably the best. Let them know about what your goal and idea is on instagram. I have a friend who did something on instagram and two things I remember that helped him big time is first he had a nice following of people. And he had also had a great goal and idea for his thing on instagram. Another thing is to join a few networking groups and groups that focus on social media.