When I was brand new to the GF diet I went to my local health food store and bought 6 or 7 mixes and spent $50.00. I wanted to see what gluten free food tasted like before I got too invested in the idea of eating that way for the rest of my life. There was only one mix that passed the mark in my book as something I would eat again. It was disheartening. I can now convert almost any recipe to GF and have most of the ingredients on hand to do it without making a trip to the store first. I have since found that I can create a much higher quality product and spend less if I just take the few extra minutes to assemble the dry ingredients myself.
The basics to have on hand are:
White rice flour
Brown rice flour
With this basic start I was able to try many recipes and develop a few that I used weekly. The bottom line for me is that it is easier and less expensive to make my own, and they taste better!
A few ideas I have found that save time are as I mix up a recipe to measure out the dry ingredients twice, the second time around into a large baggie. Then half the work is done the next time I make that recipe. I also have learned that my freezer is my best friend! Waffles, enchiladas, soups, rolls.....there is almost nothing you can't make a large batch of and store some in the freezer. Another timesaver is making your own flour mixes. I keep 2 on hand, Bette Hagman's featherlite mix for cookies and my own bread flour mix for breads and rolls.
To answer the question, mix, but make your own!