One of the only gum paste flowers to be covered in Wilton's Course 2: Flowers and Cake Design is the pansy (the other one is the Play-Doh-esque Button Flower). If you've never played around with gum paste, the pansy is a good candidate because 1) the supply list is relatively short, and 2) the end result actually almost looks like a flower found in nature. You'll need at least two colors of gum paste (one should be yellow, for the center) which should be stored under plastic cups to keep them from drying out while you're working with them, Crisco (to knead into the gum paste if it's drying out), a container of gum glue adhesive (a pinch of gum paste dissolved in a tablespoon of water), a small brush, a dusting pouch filled with a 50/50 mix of powdered sugar and cornstarch, a pansy cutter (any 5-petal cutter will do), the knife and ball tools from Wilton's 10-piece Fondant and Gum Paste Tool Set, a 3" flower forming cup for each pansy, a gum paste storage board (use the back side for your work surface), and a 9" fondant roller. You'll also need thick and thin pink shaping foam. You might also want Color Dust (in particular, Purple) to add detail to the petals.
the ones made from royal icing (one of my favorites to pipe).