First of all, you need to make an understanding the fact that there are two basic concepts of promotion:
SEO (site optimization for search engines) and Contextual advertising (paid impressions in Google Adwords and other services). Both strategies are correct but they are different in speed and continuity of the result.
In other words, he "context" brings customers quickly, but as long as you refill your account with Google Adwords. SEO will bring customers to the website later, it's possible only for a few months, but for the transitions of potential customers no longer need to pay, and even if the website does not engage in a certain time, it will have inertia and still bring customers.
The best way is to start optimizing the website, then launch a contextual advertising, it will start to bring customers, and in the meantime, continue to engage in SEO (Search Engine Optimization).
SEO includes the whole complex of work and the website itself (semantics, texts, code optimization, site speed), and over links to the website from the outside (articles, links, catalogs, forums).
Contextual advertising. It represents the first launch of an advertising campaign (we will prepare it - ads, semantics, optimization). Then, on a regular basis, for example, you need to refill your Google Adwords account monthly (depending on industry competition) and continually optimize your campaign to find cheap and massive sitelinks.
You can also consider a completely inverse promotion option. You are willing to allocate for promotion, plan the most effective actions according to your budget.