There are quite a few supplies. You might be better off purchasing the Student Kit. Other supplies in addition to the student kit: practice board, meringue powder, parchment paper triangles, ready to use fondant, piping gel, Tips 1, 2, 3, 5, 16, 27, and 104.
You'll definitely need your course 3 kit. I'm sure each course instructor runs things differently. In our first class we had to bring an 8" or maybe it was 10" iced cake and 80 white apple blossoms. We did a cake out of the book with apple blossoms and string work.... a lot of cussing in that class. She gave us the recipe for MMF in that class, and we made the gift cake the next week. In addition to the kit, you'll need fondant, a rolling pin or fondant roller, some shortening, a pizza cutter or fondant cutter. There is a list in the course 3 book, and if I remember right, the list for the second class was pretty accurate. We never learned the fondant roses though. Have you gotten the book yet? It should be helpful. Good luck! 
I had my first Wilton 3 class yesterday. We used:
the Student Kit (several of the tips, the Cake Decorating Guide, and the small flower cutter)
Practice buttercream--stiff, medium, and thin consistencies
Practice Board
several bags
Wilton fondant (the small box is more than enough)
Toothpicks
Clear Vanilla
Gel Colors
Crisco
For next week we have to bring a 2-layer, iced, 8-in cake along with the rose centers we made last night and our leftover colored fondant...and the bow patterns from the course guide, laminated. There may be a few other things but I can't recall right now.
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