For starters, you are going to need to be playing the officer class. Officers special ability is battle command which depending on how it is customized by players can boost health, abilities, or cooldown. I highly recommend purchasing the improved battle command in the collection section of the menu for 40 crafting parts. This upgrade makes a huge difference in a number of people you are able to boost at once as it increases the area of effect.
This will take some grinding but not more than some of the other class-based achievements.
Note you can only boost allies in front of you in a limited range, on the battle command icon it will indicate how many people you will boost icon when activated try for threes and better.Use battle command +Update: I have been informed that the number of people boosted doesn't matter only using the number of times the ability was used to boost 1 or more people. So just having one person in the range and using the ability a total of 100 times will award this achievement. Playing the officer class you should be able to squeeze out at least 10 per match of galactic assault.