I think posting is an underrated feature for SEO, I've seen results right away. And while fresh/new is important, the posts stop showing after a week, so repeating the same content every week is a proven tactic. For my accounts trying to do a lot on GMB, we do 7 weekly posts and rotate, and it works in most cases. YMMV, vertical/competition of course being relative.
New advertising option:
A review of your product or service posted by a Sterling Sky employee. This will also be shared on the Sterling Sky & LSF Twitter accounts, our Facebook group, LinkedIn, and both newsletters.