I too have been thinking over this question since I am planning to sell online as well in the near future. However, there are several paths that can be taken in the world of digital marketing.
A lot more information would be needed about the exact product that you are trying to sell, e.g. by 'user', do you mean to refer to a paid customer or just an interested lead? What sort of skills do you have ready to be used in order to carry out the marketing plan? etc.
I would be glad to discuss this over a call. The world of digital marketing is vast and there are lots of innovative ways in which it can be explored, but in order to plan for the same, some information about the product itself is essential.