What you are eating looks fine, just make sure your veggies add up to the full three cups.
This way of eating need not be terribly expensive and you eat much less of the expensive processed junk you used to eat. Tuna (as you have found) chicken and eggs are inexpensive and the mainstays of my day. Minced beef and sausages are less than beef steaks, and many pork cuts are not too dear. I can't say it is an inexpensive way to eat because you are generally buying better fresher food but it is certainly healthier.
