Here are two pages you may want to use with your class. The first smart board page has a gumball with a timer on it. You set the time and students can earn a gumball in the machine if they complete the task before the clock. For instance clean up and be seated in one minute. The second page is a gumball with many gumball around it to add to the gumball machine as you determine.
Click on the links to see some other gumball products in my store:
Bubble Gum Make 10 Booklet
Gumball Make 10 Add The Room
Real and Nonsense Word Sort -Gumball Theme