If you got 5000 sites to link to your site using the same keyword you'll likely be flagged for spam and attempting to manipulate the search results. That is an old-school attempt at SEOing a site that Google and the other search engines have already developed algorithmic answers to.

There are three aspects to building up your search rankings.

1) On-Site Optimization: Your site has to be coded in a way that is search and mobile friendly. You need to optimize your content for searcher's topical interest's (keywords), and give your visitors a great on-site experience by focusing on usability issues.

2) Content: You need to create and publish awesome content that fills the needs of the audience you're trying to reach. Write blog posts and create other forms of content that answer questions, provide tips, and map out solutions that truly illustrate that you are an authority on the topic.

3) Social Engagement / Links: Links are an important part of the algorithm, but getting a bunch of sites to link to you using keywords is the wrong approach. You need to be engaging on social media and (to a far lesser extent) socializing your content above. But the more you engage, the more others will socialize your content for you, which is where authority is really built.