ALWAYS if you want fully upgrade your team every time there is new stuff, at the begining of the story, and buy pets and cheer leaders after you buy the stuff from the city shop.
The actual best combo is the shaman and the mage because of the totem and the magical storm combo is the best and the mage can heal himself with life drain and the shaman can heal any one with the spring of life. Or you can take out the shaman and put in paladin so you have the revive spell.