Input about Increasing Engagement

As a mental health professional, author, and blogger, I am considering starting an FB group or another platform to blend Christian faith, mental health, and resilience group. Here are my questions: What platform would be most helpful? Should it be a public, private, or membership-based group? The primary purpose is to build my base, increase my engagement, and prepare for my next book release. While I learned a lot at the conference last year, I’d appreciate your thoughts, your lessons, and any other insights you want to share.