Hey there! and welcome!
It's easy to get lost in the world of diets, nutrition, exercise... but weight loss in principle is very easy.
Eat fewer calories than your body uses each day. That's it.
That's why so many people count their calories. It's the simplest way (to many) to calculate how many calories they eat and ensure that number is smaller than the number their body uses each day.
I would first figure out roughly how many calories your body uses each day. Then use an online calculator to suggest how many calories you SHOULD eat each day in order to create a caloric deficit (calories burned- calories consumed).
Remember that calories burned does NOT mean calories burned at the gym as indicated by one of the treadmills' display. It means all the calories it takes to move your body around, walk, breathe, organs functioning, etc.. plus of course whatever energy it takes to exercise.
It's easy to focus specifically on the exercise portion of losing weight, but I strongly recommend you focus heavily on the DIET. Creating a caloric deficit is done by eating "right"- eating within your calorie range and not more. Going to the gym, getting that heart rate up is really important for fitness, but it's not going to create the kind of deficit you need to lose weight.
(Keep this in mind: a 30 minute brisk walk will probably only burn around 150 calories. That's two eggs, or a large banana, or a few bites of cake. Barely a dent in overall food consumption for the day. It's really difficult- virtually impossible- to burn enough calories to counteract eating tons of calorie-heavy food.)
So all that said- I return to the suggestion to watch your calories. There are TONS of free websites out there to find out what your BMR is (calories your body needs a day to survive- roughly estimated) and how many calories you are consuming. Freedietingtools is one, Livestrong, My Fitness Pal, Daily Plate are a few others.
Good luck!!! With the right information and the commitment to do this the healthy way you will have great success ^_^
EDIT: PS: Like
Lovely mentioned, cereal, fruit for lunch and a small piece of meat + corn/rice for dinner is very low in calories, but it doesn't sound like enough nutrients! Where are the veggies??
I'd do a bit of online research to learn how many servings of fruits, vegetables, protein, and dairy we all need throughout the day to get the wide range of nutrients and energy we all need. ChooseMyPlate.gov is very helpful. It's really important when you're cutting calories (e.g. reducing the amount of food you eat) to ensure that the food you DO consume has all the vitamins and nutrients, proteins, and healthy fats your body needs to survive. So a quick, self-taught crash-course in basic, basic, basic nutrition will be important and helpful