What is a good strategy for building backlinks?

https://neilpatel.com/blog/9-link-building-resources-thatll-increase-your-search-rankings/

https://neilpatel.com/blog/build-high-quality-backlinks/

https://www.singlegrain.com/blog-posts/link-building/the-ultimate-guide-to-link-building-with-content/

Here are some helpful resources to increase traffic & backlinks

pingomatic
http://pingomatic.com/?oldpinger

rapid indexer sends your URLs to over 15,000 sites which gives you that many one way backlinks and Rapidly gets your URL indexed by Google!
http://www.indexkings.com/

check if your links are actually there
http://www.linkcheckpro.com/

facebook audience insights
https://masschallenge.org/media/startup-tools?ref=saasinvaders.com

17 Sites To Submit Your Products To For Traffic And Sales
https://www.viralsweep.com/blog/sites-to-submit-your-products-to/

58 directories to submit your startup
https://www.siteguru.co/startup-directory-list

You could submit your api to resource lists like https://github.com/public-apis/public-apis