Gambits are customizable commands that can direct characters to automatically perform certain tasks during battle or while adventuring.
Gambits consist of two different components, one being the "target", which represents the character/foe an action will carried out on, and the other being the "action" to be performed on the selected target. Both must be assigned a conditon before the gambit can be activated.
Assignable targets consist of party members and foes, as well as various specialized cases, for example "Ally: MP < 40%", which targets allies with less than 40% of their maximum MP. These targets must be either purchased at a gambit shop or found in treasure chests. Once you have obtained a target, your whole party will be able to use it.
Assignable actions consist of commands such as Attack, Magicks, Technicks, and Items. With the exception of Attack, your party must have obtained a magick, item, etc. before you will be allowed to assign it as an action. An action will appear in each character's gambit action list the moment it is obtained.
Always test new gambits before going into a major battle. One small mistake can turn a great gambit into a disaster. Make sure everyone is attacking the enemy and not each other. Also, check for gambits that repeat themselves endlessly, making a character nearly worthless during a fight. This is simple enough to do. Just watch each character closely and ensure that he or she reacts as anticipated. If not, consider rebuilding or reordering the character's gambits or elminate the problem commands all together.
Gambits are not necessarily always a good thing. In some of the major battles against tough enemies, it is sometimes best to use only a few simple healing and attack gambits and leave the rest up for manual input. This will help prevent you from losing valuable Mist Points (MP), or accidently using a technick or magick that has no effect on the enemy (Most bosses are immune to some of the more common status effects)
Where Are They?
You can typically find gambits in shops for a small price, however, urns and chests sometimes contain them, as well. The party can only hold one copy of the gambit no matter how many copies are found.