Food prices vary by region. And you'll benefit greatly by checking your supermarket circulars once a week. Lots of staples turn up buy one get one free, and usually they pick one meat a week to mark down significantly.
Pasta is a perfect match. You can easily prepare it in large batches, and it's dirt cheap. Just don't overdo it on the sauce if you're concerned about eating healthy.
Canned tuna is also pretty cheap, and very healthy. Look for them on sale. You don't need to prep these individually either, as you can just throw a can or two into your bag with some bread.
Soups are great for budget meals, if you get creative. I make a spice soup with a few peppers thrown in that give it plenty of flavor. Throw in some potatoes to make it filling, and add whatever veggies you favor personally. Health freaks like to go for the fresh stuff, but I find the frozen mixed vegetables are about the same and can be a good deal cheaper. I make it in a large pot and I get 15-20 servings out of it for under 10 bucks. It's also versatile as you can use whatever you have left from other meals to add to it.
Rice is ridiculously cheap, and you can find so many recipes for it. I like spanish rice with ground beef(very cheap) mixed in and sprinkled with cheese.
Eggs are great for starting the day, and come in at very low cost. Grilled cheese is also a super cheap breakfast treat. As is oatmeal. Cereals can be a little expensive(can you tell I'm a cheap ass?), but I find they're on sale often.
As far as meats go, chicken and pork tend to be your cheaper variety. I can usually get either boneless/skinless chicken breasts or the boneless pork chops for about $2.00 a pound(about 3 servings) here a few times a month. You can bake them instead of throwing them in a pan if you'd like to be a bit more healthy about it. Chicken also goes great mixed with pasta. And pork can be diced up and substituted for beef to be mixed with rice. Any leftovers can be thrown into a soup.
Beef is generally more expensive, but if you keep an eye out for sales you can find great prices on steaks. $2-3 a pound for some of the not so great cuts, but if you marinate them first, they still taste great. Ground beef, as I mentioned earlier, is pretty cheap. You can throw them into tacos or get some of the hamburger helper sides. I guess beef in general isn't going to be as travel friendly, but it's a nice change once in a while.
There's plenty of others, but I think thats enough for starters.