Out of boredom waiting to go to football i've looked through the dibs list and catchable Pokemon list. I've just made a list based on the assumed travel route of the first journey so that everyone has an idea when their first set of dibs could possibly appear:

-Route 2: Fletchling (Reeman)
-Santalune Forest: Scatterbug (Charlie)
-Route 3: Nothing at present
-Route 22: Riolu (Sully)
-Route 21: Teddiursa (Rosa) and Scyther (Mia)
-Route 20: Phantump (Charlie)
-Pokemon Village: Lotad (Rosa)