A keyword domain name, proper title, and informational site as a given ... what is the % of importance for link development versus page optimization.
On page optimization and link building go together. One doesn't work without the other. You won't get many search engine hits if you don't have your pages optimized even if you have a bunch of links. You won't get many search engine hits if optimize your pages, but don't build links. Start by getting the right keywords in your page titles, description, h1 tags, and text. Then build links using variations of the keywords.