European Escalation is on gog.com for 2,50$. Id get it cause people have been raving about it and I was thinking of getting into strategy games too anyway, wo why not use this. But would people be willing to play the original game MP with me, with 2 or 3 "Sequels" out already? Question is if Crossplay over Steam and the DRM-free version works anyway... I do prefer DRM-free games by a long shot tough...
If you're not only interested in single player (not where wargame shines) I wouldn't bother with the earlier installations at all. I understand that you prefer drm free however both the second and third use steamworks.