I'm in the same situation where I work with multiple developers on the same c5 site in my company. What we have done is to make use of the StartingPointPackage and Content Import Format which allows us to specify XML files to set up page types, pages, attributes, packages, themes and even c5 configuration options when we do the initial installation. You can check out this how-to for more details on how to make this work.

http://www.concrete5.org/documentation/how-tos/developers/concrete5...

(It's for c5.5, and will need some adaptations to make it work for c5.7)

Because these are essentially XML and PHP files, they can be easily checked into git.

We find that this method allows not just multiple developers to work together, but also makes it easy to get a base system set up on a new machine or server instantly.

I'm not sure if this is best practice, but it has worked for us, and has proven to be particularly useful at the beginning stages of the projects where we need to repeatedly reset back to a fresh install (complete with our default content and settings that we like) as we test out new concepts.

Hope this sheds some light on what you can do for your own team.