Oats, weetabix with fruits, scrambled/fried/poached egg over a piece of toast, smoothies, a bowl of fruit, a bowl of yogurt filled with topping like fruit, nuts, honey, seeds ect
Eggs, oatmeal/porridge, or yogurt are all good options to start your day with. Not only will they satiate you for the day ahead with either protein (in the case of eggs and yogurt) or fiber (in the case of oats), they are affordable. They can all be prepared the day of or the night before, making them convenient and quick, on top of being satiating and affordable.
Oats are great bc u can pick ingredients so you will not be bored or if you want to be even more quick boil an egg and it will get boiled when you are getting ready you can have a toast with some cream cheese and the egg that you boiled fruits are also great
I love to microwave an egg to over-medium and have a banana or orange to go with it. Literally takes 3 minutes to prepare and it’s a healthy balance of protein, carbs and healthy fats!