I’m not running Windows very often, so I’m probably not the best person to ask
The only thing I can do is suggesting reading this topic : Using the Windows installer for version 2.0.3+ of G'MIC
and if there is .dll missing, try getting it from the Internet, and put it right in your gmic-qt plug-in install folder. And please tell me is you succeed, and how ! Good luck!
PS: and of course, kudos to you for taking the time to see how the language works. It is not extremely easy to get into it