What state do you live in? Most supermarkets now have cake mixes for gluten free cakes. I've tried the yellow, white and chocolate cake and they're almost as good as regular cakes.
The next choice is to use gluten free flour and try to assemble a mix by using a regular recipe. Remember to add baking powder and to hold the mixture together, as a replacement for the gluten, add about a tsp of zanthium gum. This can be purchased at health food stores or ordered from online sources. It's expensive but it will last for a long time. I keep mine wrapped tightly and kept in the refrigerator.
Frostings are easy. Egg whites contain no gluten, neither do any already prepared frostings that you buy from grocery shelves.
Good luck and Happy Birthday!!!!!!!!!!