Actually, you should be going for expired domains that have very good metrics, but not necessarily that are focused on that particular niche.
Try getting something that has TF>20-30 , PA/DA>35, and it would be an added bonus, if it is social signals+extremely high quality links from news sites - this would bump up your site's authority considerably in the process.
Vetting the link profile and ensuring good, hq ones would definitely be a huge bonus for your site.