Growing a group doesn't just 'happen.'
You need to start with a good strategy. What do you want to see as the outcome of your group. We begin at the beginning, but it is best to begin with the end in mind.
You need posts centered around what you want to accomplish. Your group starts to 'work' when people join who share your vision, comment on posts and begin to start new posts.
It doesn't happen over night. But, be patient! Planting and sowing usually produces a havest.
God bless you as you start and develop a Group to help further HIS kingdom!