I used to pair the barbarian with the wizard.
Some of the expansions are quite tough, it might be difficult to source the ogres and human warriors. The wizards are all unique, so any wizard figures will do.
One thing you should probably avoid are the rules for hiring human mercenaries. They are pretty tough and quite cheap, a few of these will make clearing out most dungeons very easy for the adventurers.
Here are my adventurers.