Properly training your characters to maximize their inherent stats and skills will help you build strong parties for combat. For a large portion of the game, your party will be fixed to go along with the story, but whether forced into a certain party or creating your own, knowing who should be training what role and how to combine them into useful paradigms is the key to success.
There are six playable characters and up to three can be in a party at a given time. Each character starts with one or two roles they can research, but will quickly have access to all three of their primary roles. Later in the game the rest of the secondary roles will become available, though at much higher cost to research. Each character also starts with certain stats and a weapon, and each one will eventually be able to gain their own Eidolon in the course of the game.
Lightning
- Primary roles: Ravager, Commando, Medic
- Suggested specialization: Commando and Ravager
- Eidolon: Odin
- Starting weapon: Blazefire Sabre
Her name a mystery to all, Lightning doesn't speak much about herself.
As one of the starting characters, you'll probably want to start her out in the Commando role to deal high damage to enemies and maintain chain bonuses with the support of a Ravager. Once Fang is added to the party, however, it makes sense to switch to focusing on building her up in the role of a Ravager. Lightning is well-balanced, with high HP, strength and magic, though not the best at any of them. This combination will enhance the Ravager's mix of magic and physical attacks, as well as allowing you to switch to her Commando role for situation-specific paradigms. As a Ravager, Lightning has access to all the area-of-effect abilities, all the "strike" abilities and she has her own special Army of One ability. She can make a good Commando, but without Deathblow, Adrenaline and a unique equivalent of Highwind or Sovereign Fist, she'll maximize her potential in the Ravager role.
Sazh
- Primary roles: Synergist, Ravager, Commando
- Suggested specialization: Synergist and Ravager
- Eidolon: Brynhildr
- Starting weapon: Vega 42s
Sazh Katzroy isn't the strongest in magic and strength, although with upgrades and over time his HP gets fairly high, but don't let that dissuade you from using him, as his weapons have excellent stats to make up for it. Since he doesn't stand out in a particular offensive area, it's best to use him in a support role, as a Synergist and Ravager. In the beginning of the game, when he is partied with just Vanille, you can avoid putting wasted effort into the Commando role by using her chain gauge maintenance as a Saboteur in conjunction with Sazh's Ravager role. Although a very useful Ravager, Sazh really shines early on as a Synergist, with offense-boosting abilities and being the first one to get the very important Haste ability. Long term, he has access to all the status boosting and defensive abilities and his only real drawback is the missing Veil ability, which you'll want to acquire with one of the other characters.
Hope
- Primary roles: Ravager, Synergist, Medic
- Suggested specialization: Medic and Ravager
- Eidolon: Alexander
- Starting weapon: Airwing
Hope Estheim is the weakest character, with the highest potential for the magic stat. Along with Vanille, he also has access to all the abilities in the Medic role. His great magic will also be helpful as a Ravager with status-inflicting spells and he can get all the same abilities as Sazh in the Synergist role, except for Vigilance, though he additionally has access to Veil. Due to his weak HP, you'll want to team him up with a strong Sentinel or give him the strongest armor accessories with upgrades.
Vanille
- Primary roles: Saboteur, Medic, Ravager
- Suggested specialization: Saboteur, Medic and Ravager
- Eidolon: Hecatoncheir
- Starting weapon: Binding Rod
Early on, Oerba Dia Vanille learns some great abilities, like Deprotect, Deshell and Poison in the Saboteur role to help speed up battles. You'll also want to level up her Medic role, since she'll be your only option for a few chapters and she's one of only four characters that can learn the important Curasa ability, and one of only two that have access to Curaja. Although she's missing some good Saboteur abilities like Slow, Curse and Daze, she makes up for it by having the vital Pain and Fog abilities, as well as being the only character with access to Death. Vanille has very high magic throughout the game and better HP than Hope, so getting her highly leveled in all three of her primary roles and using her will be helpful.
Snow
- Primary roles: Sentinel, Commando, Ravager
- Suggested specialization: Sentinel and Commando
- Eidolon: Shiva Sisters
- Starting weapon: Wild Bear
Snow Villiers has the Sentinel role right from the start, and long term he has the highest potential HP of any character. Additionally, he has access to all Sentinel crystals except for Elude, which means he's one of the few who can use the extremely important Sentinel ability Mediguard. Commando is also a viable option for Snow, as he can acquire every ability except Faultsiphon, he has the special Snow-only Sovereign Fist ability, and he has great strength.
Fang
- Primary roles: Commando, Sentinel, Saboteur
- Suggested specialization: Commando, Sentinel and Saboteur
- Eidolon: Bahamut
- Starting weapon: Bladed Lance
Oerba Yung Fang is the strongest character and has access to every Commando ability. Additionally, she gets the Highwind ability that only she can use. Fang is strong in most areas, and so can be a good Sentinel, with access to almost all those abilities, and a good Ravager, with access to the four "strike" abilities. She can learn key spells as a Saboteur in their area-of-effect forms, such as Fogga and Painga, and has decent Medic abilities as well, making her a very versatile teammate for a wide variety of paradigms.