I started out with a round, flat vase that I found at the Dollar Tree for (you guessed it) $1.00 each:
I went to Hobby Lobby and found bunches of tulips that were fifty percent off. I bought about six bunches (3 yellow and 3 white) for $3.50/ea. Before I started, I cut the wire stems to about 2 inches in length and removed the plastic tubing around them to make it easier to stick them in the foam.
You'll also need, a green foam block to keep them in place (I cut the one I bought in half with a knife because it was taller than the vase), double sided tape, and I used 2.25in Christmas ribbon that was the perfect width for the vase (bought after Christmas: 60 ft. for $2.50).
2. Now begin assembling flowers.
Total cost for all centerpiece material:
Flowers (6 bushels): $21.00
Vases (8): $8.00
Foam Blocks (4): $5.00
Ribbon (alot): $2.50
GRAND TOTAL: $36.50
(Pretty good, huh?)