According to the official Steam page and PCGamingWiki , the game is lightweight and runs on older hardware: Imperial Glory - Download
You can purchase the full digital version from these reputable stores: Imperial Glory Free Game Download Full Version
The full version of is not officially available as a free legal download . While you can find a free trial/demo version on some sites, the complete game is a paid title. Where to Buy Imperial Glory According to the official Steam page and PCGamingWiki