Very cute pattern. A size 4-7 needle should work for you depending on whether you're a tight of loose knitter. Knit a swatch with about 25 sts cast on and knit for about 4 inches. See what needle gives you close to 4.5-5sts/inch measured over the center 18-20sts.stitches. The kind of needle depends on your preference: wood, metal, bamboo, etc. It's whatever you prefer.