Your story must not consist entirely of Sexual content. Being as wild and possible is allowed as long as you, the author, make your stance clear that you don't encourage the act in real life.
When you were born, do you know the ending from the very beginning, or does the ending take shape in your mind as your life progresses?
The way people write stories mirrors the way they think about life itself.
There is a method to skip this step. Write fanfics. This way, your first original novel will be a hit because your readers are already familiar with the strengths of your works. Many authors coming from SB/SV/QQ do this. @Louhi is one of them.
The trick is to write what the target audience like as your first novel to gain a followings. Then you can write whatever you want and they will read it as long as it's not the exact opposite of that.
Establish your user bases first. This also have the benefit of them following you into other...