Regardless of the scope of deployment, it’s important to start with some level of governance that will help avoid larger headaches later on as adoption grows.
A good place to start is defining the delivery approach, user groups, and ownership of key components. Microsoft provides some pretty good guidance for this in this whitepaper.
There are quite a few elements to consider and plan for related to your governance framework including organizational structure and operating model, delivery structure, roadmap/portfolio, intake/backlog management, change management, communications, and much more.
For Power BI specifically, some key elements include: