From my experience, it takes a minimum of 2 iterations for a page to rank onto page one. Assuming that the content for your webpage is based on keyword research, it will eventually begin to rank in the SERPs.
Most pages will appear in position 30-50 after its initial crawl. Then Google will shuffle it around for a number of weeks to see how it compares to other pages that compete for the same keyword.
Once a page begins to rank, the first iteration of on-page optimization should take place. This involves running Keyword Density and/or TF-IDF against relevant ranking pages. The second iteration takes place when your page is on page 2 of the SERPs.