I am on a gluten free diet, I have Type 1 diabetes, and a vegetarian, so I think I can be of some help. First thing: don't panic. There are plenty of foods that your friend can eat, and I can see by your profile that you live in California, where you can find many stores that sell these products. There are also hundreds of web sites that have gluten free recipes. Because, I don't know what types of foods your friend likes or eats, just start searching on the web (there are some great blogs and support groups) and you will be overwhelmed with what you will find.
Now the bad news: forget inexpensive gluten free foods.
You are not going to find them, and if you do, let me know. Best of luck, and I know it seems quite difficult at the beginning, but you will get used to it in a very short while.