I have read many resources regarding this subject but nothing seems to be specific. Has anyone performed a complete migration from gitlab-ce to gitlab.com, for example all data? What in your opinion are the recommended steps?
You won’t be able to do a DB restore or anything like that. The simplest and easiest way, is on gitlab.com do New Project --> Import Project, and then give the url to the project on your self-hosted and import that. Then repeat for all other projects on the server.
That’s really the only way I think you are going to be able to do it.