These boxes seem promising and helpful for now.

2 credits= 8*2= 16
3 credits= 13*3 = 39
4 credits= 13*4 = 52
5 credits= 9*5 = 45
6 credits= 1*6= 6
7 credits= 2*7= 14
8 credits= 3*8= 24
9 credits= 4*9= 36
10 credits= 1*10 =10

Total: 242 Credits in all (think I spend 9 free credits on a double crystal box)

What important for me is the:

Attic Giftbox (Really need)
Battle Giftbox (Maybe later)
Double Diamonds Giftbox (Really need)
Elite Gym Giftbox (Really Need)
Genie Giftbox
Gym Giftbox (Really Need)
Ice Caves Giftbox(Maybe later)
Missing Food Giftbox
Missing Learnable Giftbox
Missing Photo Giftbox
Missing Plate Giftbox
Missing Plushies Giftbox
Missing Transformations Giftbox
Missing Wardrobe Giftbox
Missions Giftbox (Really Need)
Monthly Checklist Giftbox (Really Need)
Operations Portal Giftbox (Really Need)
Poison Pit Giftbox (Maybe later)
Quests Giftbox (Really Need)
School Giftbox (Really Need)
Shop Pricer Giftbox (Maybe later)
University Giftbox (Really need)
Whirlpool Giftbox (Maybe later)