There exists one walkthrough made by Bruce Geryk that guide you through early game, but I think it stops before you reach any of the powerful spells. So you learn the basics of playing, and some strategies for the early game, but mid- and late-game are left for yourself to think through.
And I suggest playing against AI until you can defeat the first AI nation that goes for you in singleplayer. If you can do the same while defending yourself against two or three other AI nations you have much better chances, but it is easier to learn by losing to human than by winning computer.
