A follow up of:
As stated in the previous trophy's strategy/solution, this is actually requesting you to complete Crew Episodes to unlock more allies. You will not be able to acquire enough allies to do their episodes for until you complete Chapter 4, Episode 3, but you will come very close to the full roster of 57 by that time. For the remaining, you'll have to complete the True ending requirements, complete that chapter, and then start completing the rest of the Crew Episodes.