Yet another new person with a question...

[Squirrelloid]

I can't understand recommending MA Ulm to a new player. The nation is so bad it makes me cringe just thinking about it. All that heavy armor amounts to nothing when they start fainting at the first sign of combat. MA Ulm should have a label 'for masochistic experts only', its totally unplayable for a new player. (And lets not start with the 'zillion types of slightly different infantry' syndrome. MA TC has the same problem, and doesn't get a recommendation from me for the same reason despite being leaps and bounds more playable.)

MA Man is, however, perfectly playable against the AI by a new player. Its cavalry is excellent and longbows are very effective, meaning you can fight the AI off just recruited units if you choose. But it doesn't offer much range of play experience.

But if the new player wants to experience a range of play, I think Nieflheim is quite possibly the best choice. Very forgiving of mistakes as rdonj said. Against the AI, Nieflheim can almost do no wrong. Which means the player is free to experiment with game functionality and not be too worried about getting hosed.

After giving Nieflheim a go and becoming familiar with the basics, I'd probably play one of EA/LA Mictlan or EA Ermor.

-One of those two Mictlans should be played with F9W9 minimal bless just so you can experience the other end of sacred performance (turbo offense to the Niefl Giant turbo-defense), and of course Mictlan is all about the blood magic, which against the AI a player should be able to experiment fairly freely with since they'll have a pile of jags keeping the AI from interfering with whatever else they're doing. Now, Nieflheim could dabble in blood, but they can't afford it quite like Mictlan can afford it. Basically, Mictlan gives them a totally different play experience.
-EA Ermor is a great nation for experimenting with communions. You've got a good basic troop, the principes, which will handle all your expansion for you just fine, and stay useful against the AI all game. And you've got powerful recruit-anywhere astral-capable mages to try out communion mechanics with. To top it all off, EA Ermor can afford an awake pretender so you can try a RB researcher or an awake SC and explore your pretender options more fully. (Now, EA Ermor is on the weaker end in MP games, but that has almost nothing to do with its performance against the AI).

Once you've played those three nations, you've learned just about everything SP can teach you. (Ok, except for 'how to expand effectively as EA Agartha', but some things man simply wasn't meant to know).