There are a few ways to make your decision:
- You can write what you love and are passionate about. With the spark for the genre already there, it will be easier to do research.
- You can make a pros and cons list of the genres you would want to write in.
- You can go with your gut, and disregard what your friends and family tell you, or which genre is currently popular in the market.
- You can pick the most marketable genre. This could be tricky though, as you have no idea where the market is going.
In the end, it is up to you to choose the genre you write. No one can choose for you.