Even though Docker is available across all platforms, there is a difference, and if you want peace of mind, I recommend to use Linux from the very begining.
In my case, I wanted to use Docker to set up Jenkins on a remote Linux server) and planned to use Docker volumes for persistent data storage. It appears that volumes in Mac OS are placed in some files, and I don't know how to access them (in Linux, volumes are easily accessible in directories). So, my plans to do a test set up on Mac OS and then migrate the docker volume to the server are gone. I have a couple of VMs with Linux and can easily switch to one of them.
Having this experiance I recomment to learn Docker on Linux, don't study it on Mac or Windows. If you use Docker on the server side in the future, your servers will likely run Linux.
To start with Docker, I highly recommend this course by Nigel Poulton
