Don't feel like you have to set up an account with a wholesale florist and use half of your annual budget just to supply your students with floral material. Never be afraid to ask for donations of floral supplies. You'll be surprised what sort of "projects" parents and friends have at their house but just never got around to using and just don't want to throw the supplies away. There are other creative ways to stock your classroom with supplies.
This should be a great start to get you up and running. If you teach floral design, then you are already creative so just use that creativity to locate free/cheap materials that will benefit your students and your chapter. Creating students with high level skills in floral design is based largely on experience. Do everything you can, in every way you can to get your students creating a arrangements for all types of settings and you'll be amazed at what they can accomplish.