What are best practices for developing your career if you're the only PMM at a company?
A best practice for developing your career, no matter your role, is to network.
Building your internal and external network (meeting with people in similar roles or one you'd like to be in) will help you grow by learning what they are working on and how they are solving problems. You can use these learnings to figure out how to tackle the hurdles you're currently facing.
When you're ready to move to your next opportunity, you can reach out to your network for help.
Some ways you can build your network:
Join groups where you get placed with a random member for a 1:1 session.
Contact someone in your role at a different company or one you'd like to move to on Linkedin.
Go to in-person networking events.
For building internal networks:
Schedule monthly 1:1 with cross-department teams
Make sure you participate in the company events