Oat porridge is fantastically cheap, and as healthy an option as a cereal can get. Try to train your tastebuds to not need sugar, but if you are weak for sweets then add a little honey, diced fruit or berries, jam, or molasses. I enjoy mine with a scoop of protein powder mixed in. Coupled with oats high protein content (For a cereal grain) and you get a far better glycaemic response, remaining without hunger for longer.
I have recently bought Stevia that I can use as a sweetener for things, but sugar and oatmeal with sadly both be off limits once I start my new diet come January. Though I can definitely see about trying the idea of mixing protein powder in while I still can.