Unable to purchase gems, dragon coins, or food on Dragonvale.

What happens when you try to buy items, does the buy button not work, do you get any error messages ... ?

If you are getting a message to contact iTunes support then you can do so via this link and ask them for help (on these forums we won't know why the message is appearing) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption

If it's a different problem ... ?

See you duplicate thread : https://discussions.apple.com/thread/5093453?tstart=0

It's quite possible that you will be able to do the same purchase on a different device, but you will need to do as the message says and contact iTunes Support in order to resolve it.

I'm having the same problem on dragon vale. I'm using an Iphone 4. When I try to purchase things an error message comes up. it reads:

This is not a Test User account.

Please create a new account in the Sandbox environment.

[Environment: Sandbox]

What does that mean??

Try tapping on your id in Settings > Tunes & App Store and log out of your account and then do a soft-reset (i.e. a reboot) : press and hold both the sleep and home buttons for about 10 to 15 seconds (ignore the red slider), after which the Apple logo should appear

Then log back into your account in Settings > iTunes & App Store and see if you still get the error.

What does the error message say?

You could make this easier by providing more information.