There is no one answer for how much you should feed your bird, you should try watching how much your bird is eating and how much is wasted.
Different sized birds and different species consume varying amounts of foods. You may have to experiment until you find the right combination. For example, you can try feeding your bird a couple of meals and a snack and see how much it actually eats.
Different species of birds have different dietary needs. Some species only eat plants, some have a diet based on grain and seeds, some on fruit and some are omnivores. Each bird species has different nutritional needs.