Retargeting: Each platform offers retargeting to help you reach people who’ve already visited your website. The benefit of retargeting is that a conversion is more likely when you know the prospect is interested. You might also upload an email list and use Facebook Custom Audiences to serve ads directly to subscribers. In the following example, we see two ads that show in the Facebook sidebar to reach former web visitors.
Having large groups of content that all revolve around the same topic will build more relevance around keywords that you're trying to rank for within these topics, and it makes it much easier for Google to associate your content with specific topics. Not only that, but it makes it much easier to interlink between your content, pushing more internal links through your website.
Cost and Sustainability. While it’s not totally free and easy, SEO can be more cost-effective in the long run as it will give you a targeted and relevant results that you are aiming for your business. With regards to sustainability, even with the smallest of a budget, you can still develop a plan that will still give you the quality of results and still keep the traffic that your business is getting.