Wargames for beginners? Panzer Corps is a nifty remake of the old Panzer General games. There is also the fanmade remake called PG Forever. More recent additions to the genre that are easy to get into are Unity of Command (Panzer general with supply routes) or Decisive Campaigns: From Warsaw to Paris. That last one is much deeper but still very accessible.
Achtung Panzer: Operation Star mixes both a turn based campaign with real time battles on the east front. Best looking wargame around and great fun to play. Does have a little learning curve but you'll get the hang.
Oldskool wargames that are very easy to get into are the Battle Island games. The entire series can be found collected on GoG and is very neat.
John Tiller also made a number of great and easy to get into wargames. The Campaign series collection is old but amazing with the eastfront, westfront and pacific all covered. It's massive and one of my all-time favourites. There is also Panzer Campaigns of which I particularly like the Smolensk '41 and Kharkov '43 ones. Squad Battles is all about small scale engagements. Advance of the Reich and Winter War are both great. Red Victory is rumored to be very good as well but I haven't tried that one yet.
Hearts of Iron III by Paradox is a fun WWII sandbox to play around in with tech, diplomacy, industry and all covered. Quite fun and very accessible.
Strategic Command: World War I is also rumored to be very nifty and large scale. Have not tried it yet myself but heard very good things about it. War in the East is the defenitive wargame on the eastern front by legend developer Gary Grigsby. However it is massive and has a manual running in the 100's of pages. I wouldn't recommend it for a beginner. War in Russia is its forerunner and not as massive but also quite archaic. Then again, it's free.
