To prepare homemade gluten free doughnuts you need recipes and techniques. I needed to study the techniques first — I had never made any type of doughnut. I found these three articles helpful: chick here and/or here and/or here.
These articles contain recipes but those recipes are not gluten free. Use these instead: click here if you are interested in buttermilk doughnuts. Click here for doughnuts that are totally grain-free. You may find this article useful.