Buying In Bulk
If you have the space buying certain items in bulk is very cost effective. We eat a lot of oatmeal at our house. I have been buying gluten free oatmeal from a small family business based in Montana for quite a few years.
Oatmeal is gluten free as a stand alone. The reason this is truly gluten free is that it is processed in a factory in which no wheat is stored or used. If you have a gluten allergy you know how important it is to avoid cross-contamination. The shipping is also reasonable. They sell a variety of gluten free flours.

This was my latest order to arrive.