Seconded. I would have issues that kept getting worse as I got older. I noticed that whenever I did keto, I felt much better. When I combined it with going gluten free, I felt amazing. Well, dad gets diagnosed with Celiac and my old DNA test results mentioned I was a carrier and more likely to develop it. I haven’t had the endoscopy yet, but it’s pretty likely. This sucks as I love bread and baking it.
Anyway, if gluten is an issue, rice flour can be used for a lot of things and corn/potato starch is a good thickener (whichever is cheaper where you are).
soy (in the form of edamame, tofu, and natto) is probably the cheapest option. Eggs are usually next on the list for people over here.
Edit: seafood might or might not be an option before eggs depending upon where one lives. Organ meat as well as we eat heart, liver, etc. a lot here as well.