I tend to avoid trying to make sandwiches, I find GF substitutes a bit like vegetarian "fake meat", never up to the original. however i do have a bread maker that has a gluten free option and the loaf is quite good. it doesnt last well, but i tend to freeze half, in ready to use slices.
Have you tried the Coeliac society web site, it has lots of useful ideas?
instead of sandwiches i use potato and make a salad with the same ingredients.
I also love polenta, not the ready made stuff, but the quick cook variety. i use it instead off pasta, chopped into sauces.
I also eat it sweet, with fruit, like porridge; but its not for everyone!