Write What You Know or Are Willing to Learn
Write what you know. Incorporate experiences and characters from your past to add depth to your fiction. You’ll immediately be more connected to the content and your reader will feel that.
Or
Write about what you don't know. Some of the best writing comes from deep research. Choose a topic that you don’t know much about and then commit to research so that you may write a stronger story.
Most writers use a combination of both in their stories.