What you need a monetization specialist also known as a pricing professional. There are people who are 100% specialized in this skillset for a reason. It's hard. If you want to learn to do it yourself, I can recommend some books. Otherwise, you can going to need to speak with me or a peer with the same skillsets. Anyone recommending Freemium as a model likely does not have the ability to help you. Happy to discuss further, without understanding the app, I can't provided direct recommendations.