The first question I would ask is: Is this your passion which you are converting to a business model or are you looking for a profitable business model to enter and develop the passion? [Either way you need a passion]
If the answer is former, then you clearly have the answer. Follow your passion. You might be a small player today but as you deliver great results to your clients on your passionate topic, you will slowly turn the stones and add more people who can broaden your company's offerings.
If the answer is latter, you need to look at the competition and entry barrier in each of the varieties and choose the most profitable and less encroaching ones to start with.
The decision to be B2B or B2C again depends on the choice you make and happy to go over them over a call.