I personally think this is my order:
Rarity (she owns a store and has an adult-like personality and figure)
Applejack (she's hardworking, dependent, works on a farm doing chores and doesn't mind that at all)
Fluttershy
Twilight Sparkle
Rainbow Dash
Pinkie Pie (most likely to be the youngest in my book judging by the fact she's immature, childish and random)