Role-Playing
"The storm is here!"
Lightning is an excellently well-rounded and versatile fighter. Her three main paradigm roles involve melee damage, magic damage, and healing. These are all my basic roles in a team, meaning that Lightning can fit in anywhere. The only problem with being so balanced is that she does not excel at any role in particular.
Commando
The Commando is an offensive role using melee attacks and non-elemental magic. In the first half of the game, you will find yourself using Lightning in this role primarily. It ties with RAV as being her strongest role. Commandos give the party a bonus damage boost. In terms of chaining, COMs are important for preventing the stagger bar from draining too quickly. Sometime around the Gapra Whitewood, she should learn Launch - an extremely useful COM ability in which she launches a staggered enemy in the air, dealing more damage and preventing the target from retaliating.
If you put Light in COM mode on AI behavior, she will attack relentlessly. She will not, however, follow the leader, so it would be difficult to control what target she takes on.
The Commando role color is red.
Ravenger
The Ravenger is an offensive role that focuses on elemental magic - basically, your resident Black Mage. This ties with COMs as Lightning's strongest role. RAVs cast spells that correspond with what the Libra scan tells them is the enemy's weakness. In terms of chaining, they are responsible for boosting the stagger meter. Though you will play Light as a COM for the first half, it is likely that you'll play as RAV for the second half of the game. Her RAV role holds her unique, special ability: Army of One (Scene Drive in JP). This attack dishes several fast, consecutive sword attacks on an enemy.
If you set Light as a RAV on AI behavior, she will follow the team leader, attacking who ever they are attacking but with elemental spells.
The Ravenger role color is blue.
Medic
The Medic is your average White Mage - healing life points, curing status ailments, and reviving KOed party members. Lightning makes a good backup or secondary medic. However, she is not as good at healing as Hope or Vanille. She knows the basic healing and reviving spells early on, but she learns the higher curing spells much later than the Hope/Vanille. The only times I use her as a Medic are in times of desperation, when Hope/Vanille are dead or struggling, or with the Combat Clinic paradigm (a highly defensive setup). If you want to make her your primary medic for the entire game (which is not recommended...), she has a weapon family specifically for that called Lifesaber.
If you set Light on MED with AI behavior, she will set healing red and yellow lifebars as her first priority. After that she will raise KO-ed partners, heal status ailments, and continue healing health bars, in that order.
The Medic role color is green.