[Belcarl]

Well I'm not really a vet, but anyway.

The basics in a no particular order:

Any commander, even independent ones, with atleast one level of Holy can reanimate undeads. So take advtantage of this and recruit lots of priests outside your capitol to make expendable chaff troops.

Your best low level thugs would be Banes, Conjuration lvl 3. A good chasis with enough MR to resist banish from low level priests. A lucky pendant (5 astral gems) and whatever 10+ damage weapon you can afford will make a good thug against anything that doesn't have trample. Doom Glaive being a favourite of mine. This works until lvl 7+ summons shows up on the scene anyway.

Conjuration lvl 2 also gives you Dark knowledge which should help in improving your death gem income.

Enchantment lvl 1 will give your mages the ability to spamm undeads on the battlefield. lvl 4(?) gives you Behemots.

A well known battlefield tactic for Ermor and Pythium is to make a large block of Principes and place an astral mage or two in the middle. Then cast the Alteration 3 spell Body Etheral. This gives you etheral troops with armor and good stats! Give the principes the order to Fire closest, they will throw their javelins at their closest target and then engage.

You need to make a deciscion what your Middle/Late game is going to be though. Either you invest in astral magic with Thaumaturgy at lvl 5+ for Soulslay and Enslave mind spells. Or you try to get Conjuration lvl 9 and bring out some Tartarians. There are some nice Death evocation spells, but I have yet to train evocation beyond lvl 3 with ermor until turn 60+, thinking that Conjuration or Enchantment is more important for them.

Death and Astral spells are your strenghts. Etheral principes with some decked out banes as a vanguard, a horde of low undead chaff to wear the enemy down and all of them backed up by 3-4 unholy priests is a pretty standard Ermor tactic.

Magic item production can be in other paths with some creative pretender construction.

Your "artillery" will be lacking until quite well into the game. But cheap commanders with decent preciscion score can be decked with scepters of command (F2, construction lvl 4) for some decent long range firepower. You will need either your pretender of an indy mage to make these though.