New player - advice on picking a faction?

Welcome Whiskeyjack. relgeant is correct in his description, if you are looking for a faction that can get into the back of your opponents force and scalpel out key solos and important pieces, have strong arc nodes and strong spell casters, he gave you the top choices.

My faction is Cryx and they are known for plentiful, cheap disposable arc nodes, extremely strong spell casters (average focus is around 7 instead of 6 that you find most places), and we have plentiful access to stealth and ghostly abilities that allow us to close, ignore terrain, ignore free strikes and a lot of casters have access to abilities that allow troops and models to move through enemy models. We have the largest contingent of incorporeal models as well.

As far as where to build from the battlebox, most factions have some sort of thread or resources that provide a beginners advice. I think there was a thread here or on www.privateerpress.com in the forums there that gave advice to expanding from the battle box.

Really your choice will be based on what aesthetic do you like and what is your play style. Most factions can do almost any play style if you build specifically to it. Pick what you like the look of, proxy some things and try them out, see what you like, and make purchases after you try things out.

For the sake of simplicity I would advise staying in the warmachine side of the game. Hordes have little in the way of arc nodes (channelers), have generally higher point costs, and fury is a less intuitive learning curve.

If you like the aesthetic I would suggest Ret. It's a smaller faction and tends to have more power in said less models. They have some fantastic warjacks with varied abilities. Many of the warjacks come with shield boxes or special guns that can pull, slam, knockdown, etc. They have some powerful casters. Super combat solos to go hunting key models. A large number of arc nodes - Chimera, Hemera, Hypnos, and Phoenix. Arcanist mechanics give them plenty of spare focus for jacks.

It's just a very capable faction. Now, that doesn't mean its the "top" faction. But Cryx and Cygnar are in quite a bit of turmoil due to their power levels. I would not recommend either just to avoid future disappointment.

It's worth noting that Cryx has "Ghost Shot" available, which, among other things, allows a model to ignore line of sight, which is of course excellent for sniping out support.

Retribution has a few instances of Phantom Hunter which is similar and even slightly better. There is also one Retribution model that has Ghost Shot, Hypnos.

Skorne also has some Ghost Shot, but less arc nodes, though their more powerful spell casters usually have some sort of arcing enabler available.

To add to what regleant said, Cygnar also has arc nodes available, though they are on the expensive side. Thorn is probably the best arc node in the game though.

I'd recommend Ret as well, though the MkIII Battlebox caster Helynna doesn't really exemplify that part of the faction.

Her boss Rahn, however, sounds right up your alley. Equipped with a veritable toolbox of abilities to move your opponents models and control the board state and usually wandering around with a posse of like-minded Battle Mages Rahn is the king of picking an enemy model almost anywhere on the board and getting it dead.

Alternatively if you can find a MkII battlebox with Kaelyssa you can head for the Mage Hunter side of things that excels at long threat ranges and buff denial. That's a nice wall you're hiding behind, sure would be a shame if my warjacks could see through it. Great armor buff you have their, hope nobody takes it away or just ignores it completely.

Lot's of good stuff here.

I'd like to reiterate something Tiberius said above.

While these are great overall descriptions of the factions, most factions can be built to suit any play style.  So look for a faction that can cover your playstyle, but also pick one whose aesthetics you like.  You'll be spending a lot of time cleaning/gluing/etc, and it really helps if you like the look of your models.

I play Protectorate, and when you said you liked targeting the support in the backfield, two options come to mind:

1) A Severius 2 gunline.  Severius and a bunch of ranged jacks. Sevvy is a major spell-slinger, can cast one free spell per turn and he even has his own character arc node that buffs one spell's damage output per turn.  His 'Awareness' spell allows his jacks to see through clouds, forest and other models.

2) Thyra with all the Daughters of the Flame.  The Daughters of the Flame models (including Nicea and Thyra herself) are fast, have a high DEF, stealth, Acrobatics and Parry.  So they can be hard to hit on the way in and can just charge over the enemy front lines unscathed to get to the softer targets in back. The actual Daughters of The Flame unit do an automatic 1 point of damage and cancel tough.  The whole package has a lot of movement shenanigans.

Does all of Protectorate do what you like? Certainly not.  But they can do it effectively.

No problem, feel free to PM me if you want to dig a little deeper into Ret.