I'd put the empire as second for noob friendliness. Them and the empire are also pretty conventional in the campaign(as in, they play similar to prior total war factions) They're also slow, but you can let the enemy come to you because you have the artillery to bombard them, or a slow, creeping advance can also do the job. Their lack of monstrous units is basically irrelevant given their specialized monster killers and stupidly strong infantry, and their lack of cavalry is kind of compensated for with gyrocopters, plus, if youre new, then cycle charging is hard to use properly anyway, and that's what makes most cavalry strong.
They have a bunch of specialized units for killing specific things(irondrakes for blobs, slayers+troll hammers for large, etc). They have powerful ranged units that can look after themselves vs a lot of enemy melee, they have artillery that can counter enemy ranged and soften up a lot of enemy units. All of their units except slayers have stupid amounts of armor, their morale is high and hard to break.
