Glad to see a thread about this topic as most food related threads and stories here don't seem to mention it. The whole gluten-free thing got started b/c so many people were sensitive to the gmo wheat that is grown so much in this country (=$$$). Once I realized that the non-gmo wheat grown in Europe meant the gluten sensitive could often eat European products with no problem, a little research showed how much gmo ingredients were in everything.
Most of the gmo food is altered to make using Round Up, or glysophate on the crop easy. The pesticide is what most people are allergic to. and gmo crops mean they can use a LOT of the pesticide on it.
There is now a non-gmo project which has a tag on many ordinary foods in the grocery store, and I look for it. Organic foods are also non-gmo by definition, so that is a quick way to find them, but more expensive. Watching for sales is fun anyhow.
I'm a guerilla grocery shopper when it comes to gmo and organic.