You can start off by sprinkling the dandelion root powder over moist food to get your budgies used to the taste.
If you are using it to detoxify the liver, then about 1/4-1/2 teaspoon is reasonable.
If you are using the powder to help treat testicular cysts or cancer then you should use more.
1-2 teaspoons is OK as long as the food remains moist after the powder is added.