I'm not sure how "on topic" this question is but I think that it is fun. The more of your computing that you move into Linux, the faster you will start to pick things up.

Here is something I did shortly after moving to using Linux exclusively. It requires having a spare computer.

• Set up a server with Ubuntu Server.
• Set up SSH access to the server.
• Remove the Keyboard and Monitor and do all further configuration and administration remotely. For me, this was a serious learning experience since it forces you to (1) do everything via the shell and (2) be very careful about configuration changes.
• Get to work configuring the services you want. You might consider doing some of the following
• Focus on security from the start. Configure a firewall. Secure your ssh settings. Ensure you understand what services are running on the machine and why.
• Set up client machines to back up regularly to your server or to some external media mounted on the server or create some other backup solution that requires interaction between your clients and the server.

On any Debian-based system, a file-server and web server will be relatively easy to set up and configure. An email server will be more difficult, at least if you attempt to get the type of reliable mail delivery that a service like gmail can provide.