There has been a lot of good feedback in here already. I'm going to list a few things off the top of my head which will most likely repeat a few things said by earlier posters.
The soda thing has been covered. If you drink a pop, make sure there isn't sugar/corn syrup, as thats where your calories are coming from. So either a diet/sugar free drink, or water or sugar free juice. ICE COLD. Why? Because your body uses calories to maintain its temperature among other things. When your intake is of a substance colder than your body temperature, you will use more calories to warm it up.
You need to significantly reduce any intake of fast food/frozen meals/processed foods (including, but not limited to snack cakes, chips, frozen pizzas, frozen meals, frozen fish, frozen burritos, cans of soup, boxed meals, boxed pasta meals, mac N cheese frozen or boxed, boxed rice meals, et cetera).
Why? Well the first reason is that they are extremely high in fats and sodium, they load you on starches/fillers/fats and their nutritional value is pretty much nil. You're eating foods which have been produced to satisfy a taste craving, but the refining and processing of these foods leave you with nutritional content that you can't actually digest.
White breads, even wheat breads, rices, and other starches which state they are enriched, have been sprayed or soaked with extra vitamin additives, but this is useless, as they are in a form our body can not absorb. Your best bet is to buy whole wheat and whole grain breads and cereals which have the natural form of their nutrients, which we CAN absorb.
What you're looking for is to make every calorie you take in work for you. And every calorie in processed/fast/prepared foods... work against you.
Ideally, a daily diet should include a large percentage of fresh vegetables (dark green veggies such as spinach, green leaf or romaine lettuce, bell peppers, et cetera are best) and fruits. Don't forget a moderate portion of carbs. And last, you need protein, so you want to check out a low fat peanut butter, or low fat meat (you can find 93/7% ground beef, chicken and turkey in any grocery store). The lower fat something is, generally the more expensive that item is, unfortunately.
Your OP said you were broke, and I can identify. Fast food and prepared foods become a very easy way of eating in our lives. But I've learned to budget my money and time, and I prepare very healthy meals affordably.
Starting the day, I make a smoothie, which is made of one banana (I'm a CAGger, I only buy red-taped bananas at Kroger... they're turning brown so they're reduced in price. As the banana is going into a smoothie, it doesn't matter that it's starting to turn brown), a handful of strawberries (from a 5 lb frozen bag at Sams Club which runs me about $6... a little over $1 a pound and lasts me around 3 weeks), a light sugar free yogurt (Kroger brand 39¢ a piece), half a cup of chocolate soy milk (whatever brand is on sale), a little pure vanilla and almond for flavoring.
If you want to add a bagel or boiled egg with this, you should still be under $2 a day for breakfast.
Lunch for me is usually left overs from earlier in the week. Cheap cheap cheap!
Dinner can be just about anything. But I start with a BIG salad, Because our bodies need those nutrients AND it'll help fill you up, so you will eat less of the high calorie foods (meats, breads).
Lettuce (not iceburg, as there's about zero nutritional content... ), cut up tomato, mushroom, carrots, cucumber, bell peppers, jalapeno peppers, whatever you see in the produce section of the grocery store that looks like you'd eat it in a salad, can get a few days salad out of, and is a decent price. I won't pay more than 60¢ for a green pepper, more than $1.50 for a package of mushrooms. Even better are the bags of "slaw fixings" that include shredded broccoli, cabbage and carrots. You can find these bags pretty cheap (I'll pay $1.50), there's less work for you to do, and they last about a week, AND the prices don't go up super high when the items are out of season... which other fresh produce items will.
Try different low fat or fat free dressings until you find one you like. Notes: Be aware of the sodium content, some are REALLY high. Less dressng, more tossing. Yup. Don't use a lot of dressing, use a moderate amount and have fun making a fool of yourself in the kitchen tossing the heck out of that salad. It saves calories, stretches how long your bottle of dressing will last, AND if you really get into it, you might burn a few calories tossing that salad. ^__^;;
(Okay, I'm part kidding and part serious. Sometimes I have absolutely NO desire to eat good foods. I want to run to KFC and eat all the worst stuff for me. So I pop in a cd of something that I can fun have dancing to, and it helps encourage me as I make a mess in the kitchen.)
For your main course it's up to you.
A simple one for starters is tuna casserole with cans of tuna packed in water, not oil. A can of low fat or fat free cream of mushroom soup, a can of peas, and a package of egg noodles. You've got your protein, your carbohydrates and more veggies (although canned veggies don't have the same nutritional content as uncooked, fresh vegetables and they generally have a lot of salt/sodium added).
You can easily get left overs out of this for another dinner and/or lunch. But in each meal, exercise portion control. Put however much you need on your plate, and the rest goes in the fridge for another meal.
Snacks are tough for me, as I will either do without something entirely, or go overboard. But my best bet is to keep a bag of baby carrots and a jar of pickles in the fridge at all times. I don't actually enjoy eating baby carrots, but it's something to do if I'm bored to death and want to eat (don't laugh, I'm not the only person who eats when they're bored). I do like pickels but they're very high in sodium, so I only have a max of two.
If you crave sweets rather than salty foods, find an angel food cake mix or recipe that's easy to make and has mostly natural ingredients. It's fat free, and with a tablespoon of sugar free or low sugar jelly to top off a slice, it's pretty yummy.
Aside from the actual food you're eating, keep up the walking. That's excellent. The trick to losing weight is eating less and exercising.
And something no one has mentioned, that I'm a big fan of, is telling friends and family... those you can count on for support, that you are dieting. Let them know the basic plan. And when the days hit when you're dying for chinese food or a bag of chips or whatever, either ask for them to encourage you NOT to eat that kind of thing, OR to encourage you to have a responsibly sized treat.
Just make sure you have someone encouraging you. If you need US to encourage you... just holler.