Use Branded Strategies and Techniques
If you're considering buying promotion, statistically this could actually benefit your backlink strategies.
Internal backlinks refer to links that are from pages on the exact same website. Many SEOs fail to recognize the importance of internal backlinks. They can be a powerful tool to funnel "authority", which can lead to pages that are in need. You also have full control of them, unlike external links.
Backlinks are earned every time someone quotes you. This tactic has many benefits, but high-domain authority backlinks don't come with any particular benefit. Your brand will be more prominent if you are a trustworthy source. This will also help drive referral traffic to the site.
Google, like every other search engine, has one primary goal: to provide results that answer the query. Google doesn't want users searching for "shoes for Sale" to see tons of tennis rackets.