You will need:
  This pattern is written in four different gauges: chunky to sport weight.
Yarn: 30 - 50 grams of yarn for the  headband (just look on the yarn  label for this information) and bits of stash for the flowers. 
Needles:  choose the needles that are appropriate for yarn weight
3 stitches per inch—size 8-10
4 stitches per inch—size 7-8
5 stitches per inch—size 4-6
6 stitches per inch—size 3-5
Gauge: KNIT A SWATCH (I know, I know)