I am developing my backlink strategy. Would it be better to focus on landing new sites with high authority or getting more links from sites with high authority that we already have relationships with?

 

A:  You have a few options here.  Getting additional back links from websites you are currently linking from will most likely not cause any negative or even positive changes in your seo in how Google see your links. But if you are getting good high quality traffic from your current sources keep going and drive real customers or people that are interested in your product or service. Hopefully they will give social signals and share your content on Twitter, Facebook, Pocket, G+.

The additional social shares are important to google so keep building your traffic.
You will get a bigger boost with back links from new websites not on the same set of ips.  So go out and try and find more websites that are closely aligned to your site. Ideally your new link partners will have high DA + PA’s.