I have multiple flavors of my app. How should I set this up server side? My package names are:
Largely it will depend on how you want your project to work. You can set all three up in the same console, or you can set up as two or more different projects. Either option is valid.
Benefits of same project:
Benefits of different projects:
If using multiple projects, you can take advantage of the build types support which will allow you to have different
google-services.json files for different versions. If using one project, the same
google-services.json will work for all the varieties.
Note: as CodyMace says in the comments - remember to re-download the JSON file each time you add an app!
There are things you can do to minimise risks in either case (e.g. have dev/ stage/ prod/ keys in your Database, and have similar structures underneath), but what makes sense for you is largely about tradeoffs.
If you're just starting out, I would suggest starting with one project while you're in development, and once you've launched consider moving your development environment to a separate project. Staging could go either way.