You can easily create marketing personas so you can identify with your readers / customers.
This will give you some focus for your content writing and you can get a 'virtual' picture of the people who will be relating to your NICHE
Give your personas a name.
You need to bring them to life in your mind, but write all this up on a whiteboard or in a note pad ... somewhere that you can refer to easily when you are writing or contemplating new content for your niche.
Now, it is possible that you might have a number of personas. But generally, you niche will be targeting a specific market.
You can get quite technical about this if you want or else keep it simple (I like keep it simple).
So what you are doing is building a profile of your persona. Think of what age group and gender you are targeting. Build your profile around this.