I totally understand your concern. I got celiac when I was 21 and dead broke– like $10k a year while in college/grad school broke. Here are a few tips–
1) Do you have a Trader Joe’s? If so, their rice pasta is cheap ($2 a bag), as in their Girlfriend oatmeal ($4 a pound). I couldn’t survive without it. If you don’t, Wegman’s is a great option.
2) Don’t try to change your old recipes to be gluten free. Instead cook naturally gluten free food. It is way, way less disappointing and way cheaper. In a typical week, we make:
a)sweet potato risotto
b) black bean, tomatos, peppers, avacados, and cheese in corn tortillas
c) rice pasta with spinach, cheese, and tomato sauce
d) grilled chicken (marinated with lemon juice and pepper), grilled tomatoes, and grilled sweet peppers
e) homemade mac and cheese (rice pasta, 1 1/2 packages of shredded cheese, dash of milk, paprika)
f) meatloaf (ground turkey, sage, crushed tortilla chips, egg)
g) baked potatoes with brocoli and cheese.
As far as fake flours– figure out if you need gluten (the thing to make it chewy) or not. If you are making a floured piece of chicken or fish, masa flour (in the mexican section) is super cheap and works excellent. If you are breading something to fry, masa, egg, and crushed tortilla chips work great.
We skip sandwiches for lunch and instead do leftovers. Way cheaper and tastes so much better.
If you are really broke, black beans and cheese with tortilla chips is a great nacho meal.
If you post some food you normally eat (and hit the reply button to this so I see the notification), I would be happy to send modifications to make it Girlfriend and cheap 🙂