If its going to be a self-hosted, checkout - GoCD by ThoughtWorks, it's simple, easy to use, super flexible in terms of setting up pipelines, I personally loved using GoCD (also it's free & open-sourced!), I would say GoCD is a solid and better alternative to Jenkins.
There are tons of PaaS kind of services for CI/CD, my personal favorite has to be Werkcer for personal projects, again super easy to use, else TravisCI is sufficient for me.
Also a side-note, if you have your repo hosted on GitLab, they have their own CI, which is similar to TravisCI