what is the needed average number of well-optimized blog posts to publish on a site for good Seo performance and page ranking?
The answer is much more complex than giving you a number. You could publish a thousand posts and still get zero traction or publish one post and get traction. I have 10 well written unique posts on my site. Only one of them drives any decent traffic
Make sure all the keywords you need to rank for have quality, long copy on page and run the page through and SEO check, edit as needed against top ranking competitor sites. It’s isn’t about blogs its about content. A keyword should only have one anchor page. These responses surprise me. Stop spinning your wheels on quantity. Double down on the high volume keyword.