Hey Raggie,
I'm no expert, but I have $.02 like everyone else!
IMO, $30 a month is a challenging target. If possible, consider examining your budgeting priorities. For example, if you payed for cable TV, I'd suggest cutting that and putting that towards food. Eating well is very critical to your health. That said, I understand it isn't always possible to spend what you'd like.
While you've already gotten a lot of great advice, I'd like to repeat some of it.
Most importaintly, don't always eat the same thing and make sure you get a balanced diet as possible.
While tempting, I'd very much try to avoid processed foods like mac and cheese. They aren't that great for you and if you eat a lot of them it is going to be hard to stay health and at a reasonable weight. That said, I'm not suggesting to never eat them since variety makes everything easier.
As said before, rice and (dry) beans are a good cornerstone. I suggest dry beans because they are cheaper and they go a long way. You an also easily use just the amount you want and not waste any. Soak the beans overnight before you cook them for best results. The other nice thing about beans is that there are a wide variety. For example, you could have black beans one night, lentils another, pintos another, small red beans another, etc. You can also vary the rice using white rice some time, brown others. There are quite a few different types of rice, however, some of the fun ones like wild rice tend to be a bit pricy and IMO, some of the others don't taste different enought to bother. Note that rice can be purchased in quite large quantities, so look carefully at the prices and see if you can score a good deal. You should be able to store rice in a watertight container almost forever.
(Many) veggies are also reasonably priced when purchased fresh. Be careful not to get too much so they get stale before you use them.
Regarding meats, try to avoid the already frozen stuff. Purchase something, cut it up into smaller portions and then put them in a ziplock, press out as much air as possible, seal, date them with a Sharpie and freeze them. Try to use the date and make sure you rotate stuff so nothing get's too old. Also don't get too much saved up in there or you are bound to have some of it get stale. I think it would be optimal to have small (or tiny even) portions of some red meat, chicken and fish. Even a very little meat adds a lot of dimention to your bowel of rice and beans.
Also consider adding some canned tuna or turkey polish sausage as ways to spice things up. You can treat the sausage as you would the other meats, chop it up and freeze it in sizes correct for a meal additive.
When cooking something like ramen, add a few things to make it more healthy. A few fresh beans, maybe some tuna for example.
Spices tend to be expensive, but you probably at least want some salt and pepper. Note that you can purchase whole pepper in a little container with a build in grinder. Fresh pepper is mucch better than the pre-ground kind. And it just takes a little bit to add some dimention to food. I also like soy sauce and keep in mind that you can get it in larger containers and then re-fill a small container. I tend to keep a larger container in the fridge and have kept it in there for a LONG time w/o any apparent problem, although perhaps this is not recommended.
Even though they are not as good as fresh veggies, you might want to keep some frozen veggies on hand. When you are in a hurry you are less likely to omit veggies if you can just toss in a handful. I have to admit, I really like corn, and adding some corn to ramen or rice both really add a lot of dimention IMO. I also think canned tuna makes a good quick meal crutch as well.
Also consider noodles to vary things a bit. I think maybe some yakisoba noodles instead of rice sometimes makes a nice change and you can treat it the same way. Add a veggie, and a bit of meat.
Planning your meals ahead will make things much easier. It also helps you make sure you have what you need defrosted, when you need it, or to have the beans soaked when you need them. It's a real bummer to be hungry and have nothing defrosted/soaked.
Consider taking one of the one-a-day style multi-vitamins to round things out.
Good luck!
-john