I mean, you have GM privileges, so its ultimately up to you. If we started on Earth, where would the actual plot start? I mean, a SEED Destiny-esqe beginning with an operation on the ground could be a possible way to start it off. That'd give the characters a chance to see each other in combat quickly. Or we could start as everyone boarding the ship as it launches. I don't really know, I'm just kinda throwing ideas out.