I am also in a similar position. I'm about to start my internship with a startup. Their only product is an app, but I will play with the data. I plan to start it this way because most of the application requires a redesign of the UI and the UI.
I would start with an expertise / heuristic evaluation. There is no competing product, so I am canceling the competition analysis part. The next phase will be research, then design, followed by usability testing and launch.
I would like to know the opinion of the community and see if this could be a good direction.