For this pattern you will need (100g Balls):

Baby Cardigan
To Fit Chest 16"  - 2 Balls
To Fit Chest 18"  - 2 Balls 
To Fit Chest 20"  - 3 Balls
To Fit Chest 22"  - 3 Balls

Needles Needed: 4mm and 3.25mm. 
4(4:5:6) Buttons