The retribution of Scyrah is an incredibly varied army, despite its smaller number of units compared to other Warmachine forces. A good place to start in collecting a Retribution force is to determine what type of army you want. This will generally be represented by your casters, all of whom play a different style and require different units to play into their synergies.
Adeptis Rahn is your go to caster for magic smackdown and denial. He has a lot of push spells and knockdown abilities. His army should be based around these abilities and getting the most from his feat. A Rahn army should have plenty of battle mages, a few magister solos and then houseguard. Riflemen will allow you to shoot the heck out of the opponent, and Halberdies give you a nice line to hide behind that does not block Los.
Garryth is the premier assassin caster of the retribution. He is all about sneakiness and killing your opponent’s caster before she knows what hit her. Take units that support the sneakiness. Mage Hunter Strike Forces, their UA, the MHA solo and Eiriss all play well, keeping your opponent off balance and making them react to your moves.
Vyros is the Retribution’s sledgehammer. Bring him with Jacks (Chimeras and Manticores are usually the best) and Dawnguard and throw them down your opponent’s throat. No real subtlety here, you are simply killing your opponents models before they kill yours.
Ravyn is all about range. Her army should be able to outshoot most Cygnar armies. Take all shooty things with her, and maybe a squad of halberdiers to hide behind. Riflemen, Stormfalls, Hydras and MHSFs all love Rayvn and her excellent feat.
Kaelyssa is the jack of all trades. She can run pretty much anything effectively. She is great for starting players, but is pretty bland in my opinion.
Well, I hope this article provided a little help to those who are interested in starting a Retribution army. It is a really fun army that plays pretty straightforward, but has a lot of tactical depth. Good luck and happy hunting!