You will need

Cardigan
0-3 months (16in Chest) 2 Balls
3-6 months (18in Chest) 3 Balls
6-12 months (20in Chest) 3 Balls
12-18 months (22in Chest) 4 Balls

Hat
0-3 months 1 Ball
3-6 months 1 Ball
6-12 months 1 Ball
12-18 months 2 Balls

3.25mm and 4mm Needles
3.25mm Circular Needle for Cardigan
4 Buttons
3 Buttons (optional for Hat)