I wanted to start making my own flour to save money - particularly brown rice flour (a staple of mine) and quinoa flour (I like the fact that quinoa is a complete protein). Investing in a grain mill was one option, but since I decided to buy a Vitamix (a high powered blender) to increase my families intake of fruits and vegetables, I decided to try their dry blade container instead for grinding grain. I have had success with my brown rice and quinoa flour. If you bake a lot, making your own flour definitely helps reduce costs. Research your options to make the best choice for you.
You may also find gluten-free flours cheaper at Asian markets in your area. A friend of mine found tapioca starch, potato starch and white rice flour considerable cheaper at a local Asian market.
Making your own mixes saves money, too. It's easy to do and makes baking more convenient when your time is limited. Simply mix your dry ingredients together well in a bowl and store in a sealed bag. You can put it in the refrigerator or freezer if you are not going to use it right away. I like to look at product labels to find out ingredients in my favorite purchased foods, guess their quantities and try to make the item from scratch. Challenging yet fun!