I don't think any one thing is enough. Who was it said writing was 1% inspiration and 99% perspiration?

Each one of us has different innate skills, and no doubt we envy the skills that others have, which we lack. Personally, I find it easy to use words and, from the feedback I have had over time, my writing is emotional and evocative. I find it quite easy to come up with an interesting initial idea, but I find it very, very difficult to turn that initial inspiration into a full story.

Others, I know, come up with full detailed, complex plots, and find it intensely difficult to create realistic characters, or to use words to describe atmosphere effectively and so engage the audience.

Writing what you know is a good intial precept - but even that seems to me to be only a starting point: I believe your story and your characters take on a life of their own, and your imagination has to complete the areas that you cannot fill in from your own personal experience.

So - you need the lot, and the bits that don't come naturally, you just have to work at.