Hi. I am a celiac, eat gluten free and have visited Paris several times. My best tip.is to have a small card in French explaining you are a celiac and cannot eat gluten, i found one free online and carried a few copies. i also searched online for gluten free products often in bio stores, or in pharmacies. The one I use is Naturalis, they have a website, so you can find a location. The pharmacy may have more expensive things.
There is a gluten free restaurant, which I cannot remember the name, out by the canal St Martin. Easily reached by metro. Reservations recommended as it is tiny. They do have gf desserts for sale to go.
In France, I often had omelettes for breakfast, moules frites, mussels & fries many times, I often eat fries in France, as there is rarely any deep-fried food besides the frites. I did not often have dessert and did not have crepes, as they could not guarantee the buckwheat crepe would be entorely gf. I did often have ice cream, sometimes at an Italian place Amorino, they have a written ingredient list, and they will know whay is gf. Grom is the most fantastic gelato; they do have a shop in Paris. Great stuff.
I usually did not have an issue when I brought my card and was careful, for instance, i had sorbet for dessert, but it had a crisp cookie in the side. I knew I could nit eat that.
Also, go to a market if you can for fresh fruit & veg & other things like scarves. Enjoy your visit to my favorite place.