Are you building both forces? A single force? or what? Any special themes?
I am building primarily a Axis Army. Both a friend and I got the core box set and he is doing allies. We swapped 1 walker and 1 squad to bolster our main armies but retained 1 walker, 2 squads and the hero from the opposing army. We also split the figs out of Operation Cyclone and Operation SeeLowe. The goal is to have Axis force as my main army and a secondary, smaller force of Allies. Though I do plan on getting the Red Devils to bolster my meagre allies, they just look cool.
My theme is a rogue Axis command. One that was displeased not whit the assassination of der Furher but with how the nation has been handled since the event. A rogue Oberst (Colonel) who distrusts the Von Thalers and despises Sigrid and her ilk. He is a former SS Oberst and I do plan on him enlisting all sorts of nasty science gone mad forces (Walkers, Zombies, Apes and thinking of using werewolves somehow). His secondary goal (after crushing the Allies) is to rid Germany of the Blutzkreuz and its influences.