Needless to say, Google is going to make meta descriptions and meta titles short for mobile sites. So it is advisable that you should not write long Meta descriptions and titles. Else, they will be truncated by Google. Backlinks from relevant sites in your niche are also worth significantly more than irrelevant sites or pages SEO Agencies base their understanding of search engine algorithms on a set of parameters which have been shown to work on other websites; there is no formula or secret knowledge that SEO specialist's can boast, simply relevant experience and an understanding of the way the system works. Every page of your website (if optimal) represents an opportunity to rank that page and dozens more when combined with SEO best practices.