I did something similar, but for a plot-heavy fantasy story - I started my first chapter with some action that happened a few years earlier, that doesn't involve the main characters but is strongly linked to the plot and the characters meeting up. I think it's important to throw some action straight away so as to intrigue the reader and make them want to unfold the mystery.
I also think it's important to introduce the character in real-life situation rather than describe their personalities through their thoughts. I do a bit of both: The one character that we constantly follows is introduced through her thoughts, two of her friends through interaction and while facing everyday situations, and the 4th one is introduced by the rumours running about him. I find it pretty balanced that way but can be wrong 
And some introductory action happens once they finally all get together!
I think another important point is to leave some sort of a cliffhanger or important questions unanswered at the end of the first chapter, so the reader would want to read the next one 