A Gerbera daisy corsage is not my first recommendation, as a florist. Gerberas are very water loving and will wilt faster than other flowers as roses, carnations, daisies and other choices. Some brides are insistent, however, so it is important that you use a flower sealant and keep the corsages refrigerated as long as possible before pinning on the wearer.
For a corsage as shown below, you'll need the following flowers and products:
If you haven't made corsages before, check out the glued method tutorial.