While collecting your Cryx army, you will see use out of certain models again and again. Starting with the Cryx Battlebox, the following models are also solid additions to any Warmachine army.
What to Order
For a minimum unit, buy the unit box:
PIP 34019 (6 models)
For a full unit of ten, also buy two blister packs:
PIP 34010 (2 models each)
Mechanithralls are the cheapest unit that Cryx can field. Though they're clearly meant to be cannon fodder, their Combo Strike Attack will surprise an opponent once Cryx uses its various abilities to reduce the target's DEF and ARM.
Brute Thralls are cheap and can added extra punch to the Mechanithralls.
When mechanithralls are supported by a Necrosurgeon and Stitch Thralls they become a very hard to kill block of troops since the Necrosurgeon can replenish their ranks.
For starters you probably only need the unit box for a minimum unit.
A minimum unit buys you six walking bombs that will explode one after another if an opponent ignores them. Bile thralls are the bane of all infantry and single wound models. Spells like Excarnate and Telekinesis can increase their threat range. A single purging Bile Thrall can take out entire units of troops, especially ones that like to be tightly packed like shield wall units.
for a minimum unit, buy the unit box:
PIP 34017 (6 models)
for a full unit, also buy two blisters:
PIP 34018 (2 models each)
Bane Thralls are protected from ranged attacks and magic with their Stealth Ability and put out a lot of hurt when charging with their Weapon Master Ability. Top it all off with the ARM Debuff from their Dark Shroud Ability and you have yourself an elite troop.
The unit attachment is very good. If it comes down to it you will usually prefer the UA with a min unit over a max regular unit. The UA provides tough and the ability to stand up for free from knock down. This will make the unit even harder to kill off.
Another common addition is the solo Bane Lord Tartarus. He is a melee force himself, but also buffs the Bane Thralls and replenishes their ranks when he kills badguys.
The Skarlock is attached to a warcaster, and once per turn it can cast a single spell of no more than 3 focus that targets a model, friendly or enemy. While some of the best spells are battlegroup or spells that the warcaster casts on itself, the Skarlock can help support a warcaster by re-casting an upkeep spell or trying again with an offensive spell.
A new kind of Arc Node
PIP 34070 (Two arc nodes)
The Ripjaw box gives you two plastic warjacks that could be used to deal with high ARM with its Armor Piercing Ability and then it can help the warcaster channel spells with its arc node.
The be-all and end-all of heavy 'jacks
It's a heavy warjack that does it all. It casts spells, it has the advanced deployment ability, it generates its own focus, and it heals itself when it kills living models.
Familiarize yourself with these Cryx tools, and you'll find a place for at least some of these models in many of your Cryx armies.