Before you even begin to set up your niche website you need to perform comprehensive keyword research. There are many tools available for this and you can outsource the work if you don’t want to do it yourself.
Content marketing isn’t a magic bullet, it is work, and it is only effective if you consistently put out excellent quality content.
What's your story? How did you get to where you are now, and why did you begin your company? These are all important questions that will better your personal brand.