We don't offer Windows 2008 Server OS anymore. We offer Windows Server OS 2012, 2016 and 2019. You can purchase a plain Windows 2012 server OS (without any software installed like IIS, Controlpanel etc.) with 1 GB RAM. If you want to add any additional software on it, you must require 2-3 GB RAM to run the OS smoothly.
Please refer to Recommended System Configuration for Windows Server 2019, 2016 and 2012 for more details.