Collaborate is a Tier 1 skill under Jack's Greater Good skill tree.
This skill can have a maximum of a 5% damage boost per stack and still only 10 stacks. To quickly gain stacks Jack needs to run or move a decent distance and the Digi-Jack's will teleport to his new position. This teleportation will also count as a death of a Jack since it will need to redeploy. The only drawback is that this wastes the time of the action skill so to counteract this, it can be combined with Best Foot Forward where once an enemy is killed the time running to "kill" the jacks is regained once an enemy is killed.
To maximize the stacks again is to let the skill run all the way out of time because by then there will be more stacks of Collaborate. To increase stacks before a large fight, Collaborate can be activated shortly before engaging, and then each jack can be allowed to run out of health once so there are two stacks before fighting. In most cases, the length of the skill will be longer than the fight itself so it is sufficient to only have half the time when the fight begins. Again combined with Best Foot Forward skill, the time lost will be partially regained.