>>716442037OK if you're starting with games this is how I'd do it:
Space Marine 1 - quick and easy look into Space Marines, the Imperial Guard (or Astra Militarum whatever they're called now) and Orks and Chaos and how war is waged in 40k
one of the Dawn of War RTS games - superficial but very accurate look into the species and factions of 40k (even though it's a bit dated, no Tyranids and the Necrons are based on outdated lore)
Mechanicus - very similar to XCOM, very good atmosphere and insight into the Adeptus Mechanicus and the cultish side of the Imperium, also better look into Necrons
Darktide - if you want to see how brutal and severe the Imperium is, how it fights internal corruption and just what a shithole it really can be
I'd play something like Rogue Trader only once you're really familiar with the setting.