There isn't a minimum requirement for the disk size, amount of RAM, or CPU cores - but generally you should have at least 4 cores, 4GB of RAM, and 200GB of disk space; for the game servers to use.
Windows is not supported. You must have the following things:
Linux based OS
Host with Docker support
2022 open for TCP for WISP Deamon
+ IP's and ports you want game servers to use