Make webboard.org No.1-3 in selected google search results related to "forum", "bulletin board", "message board" etc.

Make https://webboard.org No.1-3 in selected google search results related to "forum", "bulletin board", "message board" etc., please contact me, propose 10 keywords from Webboard.org content and describe your methodical approach to reach the goal (changes on the site content are not allowed because I have already SEO optimized it, so you have to rely on placing high quality backlinks by facebook or forum posts etc.). There is no extra budget for payed advertising.