Hurricaine/Buffalo for the Finns is avery good starter campaign (if for no other reason than the Red Air Force pilots you will face, especially in the first campaign or two, will mostly be relative morons . . . as is more or less historically accurate). A6M for the IJN is in some ways a forgiving early plane for fighter pilots, though you (also of course), can't take much damage in it.
Just about all the US planes fall into the "BnZ" category . . . and I would actually rate an F6F campaign as about the easiest (F6F is a decent turn fighter, and the IJN opposition it faces is not as comparatively dangerous as that faced by the F4F). So 1943+ F6F campaigns would be a good bet.
Late mode (Spit XIs) can also be forgiving, espcially if you want to turn and burn. . . any of the BoE/2nd TAF/NW Europes campaigns (depending on what add-ons/mods you have) would fit the bill.