Atlantis' Secret Love of Bows
Atlantis has no native ranged troops other than the one shot harpoon your seal hunters carry (which is a javelin that can entangle what it hits... nice but of marginal use). Your enemies will know that you're going to throw a wall of icy flesh at them so they want to hit you with arrows, fireballs and the various cloud spells which make your troops and your frame rate cry. What no one expects is Atlantis shooting a continuous stream of 6+ lightning bolts at their mage line, withering entire ranks of troops to dust with banefire or blotting out the sun with 150 arrows per combat round. With Voice of Tiamat, you'll likely have a bit of air income you can't normally do much with. In CBM 1.92, Bows of War and Thunder Bows are both A1 to construct, making them something 1-in-4 of your Angakoks can forge. And every Tungalik can forge a banefire crossbow if you have the gems to spare. A trio of Tungaliks scripted to cast quicken self -> fire will fire twice per round (or once per round with the crossbows) at their enemies during the fight. Lightning bolts will put a serious hurt on large and/or high protection enemies. The Bows of War will give you the equivalent to an enormous army of archers forcing the enemy to come to you. The banefire crossbows can be set to fire closest and ruin many ranks of troops with normal life spans while leaving your atlantian infantry unscathed (an Atlantian grunt can sit through more than 80 rounds of decay before they hit old age). "But don't Atlantians have poor precision?", I hear you say. They do, but most magical bows have a huge precision bonus (such as the Thunder Bow's precision of 10) meaning that the bow is doing most of the aiming for them. Atlantians with high precision bows can even shoot in the dark courtesy of their darkvision-50. Using 5-gem bows to turn your ubiquitous Tungaliks into powerful artillery pieces is a real win for Atlantis and can really surprise your opponents.
This same "Quicken Self" + shoot-shoot-shoot approach can be used for spell casting items like wands of corrosion or staffs of numbness; allowing you to turn an uninspiring mage into a double-barreled, magical death-lobber. In a way, this allows you to save on gems and money because you get twice as much out of each magically-armed mage you bring to the fight. A little water magic can become a large force multiplier.
An Ode to Crystal Shields
In CBM 1.92, Crystal Shields were reduced to E1S1 and construction-2. This means that 1-in-4 of your forgiving fathers can forge them. For those that don't know, this shield casts Power of the Spheres on it's wielder at the start of battle... you know, in addition to being a high-encumbrance tower shield. Hand this to any Angakok and they become an H3 priest who can cast Divine Blessing and smite or simply spam banishment to better effect. Hand this to an E1 Angakok and he can cast summon earth power and lay down E3 (E4 with earth boots) combat spells. Hand this to an A1 Angakok and he can cast Wind Guide (which matters if you are fielding magical bows or dropping a lot of evocations). Hand this to a Ring of Water, Robe of the Sea W4 Angakok for some truly enormous W7 falling frosts/niefel flames. Hand this to a D3 Angakok for Darkness followed by repeated castings of drain life.
The fact is, LA atlantis has a hard time getting access to air, earth and fire boosters (and tend to have better things to spend their death gems on instead of skullstaffs) so the Crystal Shield acts as a universal booster during combat. Having a few in the lab allow Atlantis to quickly dispatch a customer-tailored caster to the battle, regardless of whether they're spamming Acid Rain, Falling Fires, Shadow Blast or just a really powered up Ice Strikes.
Water Gems, Water Gems, Water Gems!
I have come to realize that you can never have enough water gems. You get all sorts of excellent commanders (Naiads, Grendelkin, Great Kraken, Monster Fish, Water Royalty, etc.), all sorts of good fodder summons (sea dogs, claymen, kraken, sea trolls, winter wolves, etc.), many excellent items (boots of quickness, water rings, staff of numbness, frost brands, etc.) and, of course, they fuel those three crucial rituals: Wolven Winter, Ride the Currents and Traverse the Sea. They also fuel your acquisition of non-water gems courtesy of Voice of Tiamat. You should fully site search your entire domain for sources of water gems because they are the primary fuel for your magical war engine.
I also want to call special attention to Sea Trolls. They are big, squishy, size-4 piles of regerating health that you can summon once you hit conjuration-3. Once your opponents start getting serious about their ability to blast your troops with magical death, you'll want to start sprinkling sea trolls into your army to act as lightning rods. Given their low protection, high hp and large size, the combat AI loves to target them for high damage evocations. And since they're so large, their square will contain at most one other soldier. That means if one of your trolls eats 3 or 4 fireballs before going down, that's one water gem you are out of instead of 9 to 12 of your precious Arssartuts. Sea trolls also distract enemy commanders and archers scripted to "Fire Large Enemy Monsters" from targeting your size-4 Angakoks. Finally, sea trolls are poison immune which make them situationally very useful if you are squaring off against C'tis' poison slings, Patala's naga or Pythium's poison... well, everything (LA Pythium loves them some poison). They also do a good job blocking C'tis' ubiquitous, size-4, trampling bone chariots. Summon sea trolls makes an especially good use of time for any W3 forgiving fathers you have (or robe + ring Tungaliks) since summoning them is mage-turn intensive and you'd rather have your Angakoks doing something else.
Research Boosters
Atlantis is one of the few nations who can forge all three research boosting items: owl quill, skull mentor and lightless lantern. Because of Voice of Tiamat, you are likely to have and handful of fire and air gems you don't otherwise have a good use for. The fact is, because of Atlantis' lackluster research AND the fact that Atlantis tends to rise very high, very fast (often earning them a coalition of enemies if they aren't very careful diplomatically), Atlantis can find the transition from middle game to end game somewhat difficult to make. One solution is to make a concerted effort to funnel your hopefully gem-rich and certainly gem-diverse empire into your research. If you dump 50 fire, 50 death and 50 air into research boosters (doable by the mid game), you'll have spent 25 mage turns to generate an additional 34 Tungaliks of research... every turn... forever. It can seem like a painful upfront cost but research is one of LA Atlantis' real weaknesses. Hey, it can't all be dirt-cheap super soldiers and synergistic racial abilities.
Also of note, CBM 1.92 owl quill offers -2 encumbrance (which translates into a -4 fatigue when casting... the equivalent to earthpower or an E8 blessing) so they can help increase the endurance of your Crystal Shield holding Angakoks.