While the amount of content your site has is very important, even more important is the relevance of that content. If the content of a site is based on one main theme (e.g. industry, product, service) then a search engine will understand which terms it could or should rank it for. If a website is populated with content covering a number of different themes there is no focus, and search engines will struggle to give it rankings.
A good SEO consultant help to advise you on how relevant your content is and the best way to grow this to show search engines how relevant to your audience your website really is.
Whilst in bound links from other websites are important in search engine optimisation, a more important factor is to get links that are really theme and topic relevant. Search engines understand that if a site which is relevant to your industry or area of interest links to you then the content in your site is likely to ne relevant, interesting and useful.
An Expert SEO will help you source the most relevant links from websites which not only compliment the content on your site, but also help to grow your site’s strength.