My 6 year old with autism also has celiac and multiple food allergies (peanuts, tree nuts, milk, soy, vanilla, and bell peppers). He's been gluten free for 4 years now (since before his autism diagnosis actually). I have honestly found the less specialized the product is the better it tastes

We do the VAST majority of our shopping in regular grocery stores. Specialty gluten free products are expensive and rarely taste good. You just need to find a few key ingredients and then go from there. I buy gluten free flour (there are several good ones), gluten free bread crumbs (I like Gillians), and rice pasta (Tinkyada), and then the rest of his food we buy in a regular store.
I actually don't make a ton homemade... just a few things like chicken nuggets, muffins, meatballs, and pancakes. I usually make them once every 2-3 months and freeze.
From a regular store my son eats...
* applegate farm hot dogs, hormel mini pepperonis, hormel or hillshire farm lunch meats,
* Lays potato chips, Tostitos (original), Fritos, Mike sells puffed corn, and kettle corn (forgetting the brand off the top of my head), sweet potato chips, and rice cakes
* Craisins, Fruitabus, Twisted fruits, Annies gummy bunnies, Brothers all natural freeze dried fruits
* Rice Chex, Corn Chex, GF Rice Krispies, Fruit Pepples, and Cocoa Pebbles
Thats just a few examples... there's many more!! It just takes time to figure out what your child like and what they are willing to eat.