Before you start, do a little research on the marketplace to see what other developers are doing, and where you can make an impact.
For example:
Does my add-on help users to do their work quicker and more effectively?
Does it streamline the user’s workflow(s)?
Does my add-on enable users to be more creative, or make their work look better?
Are there lots of add-ons already doing the same thing on the marketplace?
Does your add-on leverage AI to generate content or automate workflows? If so, be sure to check out the Generative AI requirements.