It is very important that there be no sugar in their diet, as they are highly susceptible to diabetes...no corn, very few fruits...etc.
We get our degu food from
www.exoticnutrition.com... They get fed this, along with Timothy hay, and a healthy browse mix, which they have to forage for.
Also, one degu is not a good idea...You should have at least 2 or 3, because they are very social creatures, and will spend a lot of time talking to each other and snuggling. They also tend to be very skittish.
Look for sites like
www.deguworld.com for a lot of good info.
Good luck