But I’d say it’s one that has no sugar, is filling, healthy and nutritious. Whole foods are good.
Totally depends on your budget and what you like/can be bothered to make in the morning. You’ll have to figure it out for yourself as there’ll be loads to choose from. Experiment if you can.
I don't know that it will make you "lose weight". But, it will help keep you from gaining weight with unhealthy options, and from unhealthy snacking from a less filling breakfast.