In order to develop a good marketing system, you need to know the basics of marketing. Sometimes you need to know even more about marketing. If you hav nt studied marketing at the university, then it will take you a lot of time. I would recommend you to turn to professionals, now many companies offer this service, for example, here fuselabcreative.com/services/marketing-and-communication/ you can read more about what a professional marketing strategy can give you. It seems to me that it is very difficult to be a business owner, programmer, designer and marketer in one person, so there is nothing wrong with turning to professionals.