Seems this question is quite childish but it's reality that only project and development can't lead in market. marketing is the most !!
As you mentioned, marketing is an art and therefore you need to hire a specialized person to achieve success, just as if you were looking for qualified developers or an integrated team.
Think of it as the sides of a triangle. If it's not perfect, you won't be able to succeed.
We cannot give you ideas because marketing means spending money and of course spending money means a short-term and long-term strategy that needs proper planning, the tips we will give you will not be ideal for developing such strategies.
Nothing is impossible or beyond in marketing. Therefore, any way to make profits is possible and acceptable.
Remember: you will not be successful in marketing without money unless it is something unique that will change the world or solve a real problem.