Hi Gracee,
It sounds like you're well on your way to figuring out gfcf living. I've been gf for about 10 months now, and it was certainly overwhelming to start with.
Elana's recipes are great because they use such a small selection of ingredients so you don't need to stock your pantry with ingredients you won't be using on a regular basis.
I don't know very much about the cf diet, so some of my staples may not be appropriate...but here are the things I try to keep stocked in my pantry:
Arrowroot powder, xanthan gum, tapioca starch, potato starch, applesauce, quinoa flakes (which sometimes work as a substitute for oats), sorghum flour, buckwheat flour and teff flour.
I definitely kept my pantry simple when I was starting out, but have been trying new ingredients and experimenting more lately. I do try to plan ahead a bit so that I use up the ingredients I have before buying another type of flour, that way I can use things up before they go off and I don't have heaps of half-finished jars of flour sitting around.
Hope this helps. Best of luck!