Simply stack up skill activation boost ability. It will increased additionally with each 1.2x (or more) you have. For example, my team in a sig has 3 1.2x skill activation from Appricot, Epidendrum, and Nightmaher. So it's each girl's skill activation x1.6 times chance. Some girls like Dendrobium or Christmas Senryou can boost their own skill activation in the first turn, so They are total beast as sweeper but if they can't dispatch enemies in 1 turn, their usefulness will be toned down. This is true for any girls with 'first turn only' ability.
Not sure what is 'provoke' you talking about, if it means provocation skill, well it's best used on girls with dodge skill to migrate the damage from the team. One thing for sure, it made Saffron real broken.