Shouldn't there be some kind of basic FAQ for every nation as to how you use the units and stuff? When a Newbie like me goes and sees the whole frekin page full of units on only one nation and doesn't really know what to do, there should be some way outta that.
Basically what worked for me was looking at what each unit can do compared with the gold cost/upkeep. Then buying the commanders/mages as needed. If you are worried about computer opponents just play a larger map with fewer AI opponents.