Your business idea sounds wonderful. I agree with Tui. You have a customer base already. If you have not already done this you could design a ‘free thing’ (called a lead magnet), to offer your Instagram followers in both camps. In exchange for your valuable content that steps potential customers through a sequence of steps, you collect their emails and start building your database.
Having an ideas generation session to dream up all the ways you could serve people will help the gems pop out. There are many structured activities that can help with this stage. it’s about asking yourself and your business partner the right questions that will make your direction clear. At the same time you could survey your followers and find out what their most pressing needs are that you can help with. Write a full description of your ideal customer – focus on one person and describe them in detail. You may need a web site down the track and that is getting easier and easier to set up with very little cost. Not sure if you are seeking to attract more people to face to face retreats or online sessions with you but either way, making an offer (even with a few sponsored social media targeted ads) and building your email list are good places to start. If you don’t already have a database management system, Mail Chimp is one that has good basic functionality for free to begin with. Starting/building a small niche business takes a whole lot of heart and perseverance. Follow your deepest sense of what seems right and go that way. Wishing you all the best.