Keep playing with VMware vSphere ESXi. It is free to download and use in production environment with some limitations of course.
Keep updating
April 2nd, 2020: ESXi 7.0 released.
The official VMware vSphere Blog
Enable ESXi Shell and SSH
Just for learning, practicing, playing around with vSphere ESXi, you definitely should enable ESXi Shell and SSH, which are disabled by default.
Press F2 at the console, enter username and password to login, then go to Troubleshooting Options to enable or disable them.