D8 -- wow. That's a lot of questions.

Let's see... The most important thing in Yael's life is Vao. That's a given. And vice versa, Vao does not exist without Yael. Mathey's most important thing is his adoptive family, no matter how big it gets. Remi's most important thing was his father. Now that he's gone, his most important possession are his father's guns. Falen's most important thing should be her brother. Unfortunately, he sometimes takes a backseat to her job -- her curiosity and drive get the best of her. Griffin's would be... either the bag he uses for work or two of his earrings. Jin's would be the jewelry his father gave him that originally belonged to his mother.

I think some of these priorities change throughout the course of the story, but these are pretty important in general.