please be more specific. by 'dragon spell' do you mean becoming a dragon, creating a dragon, controlling a dragon, gaining the abilities of a dragon, a wealth spell involving dragons, a protection spell calling on dragons, what exactly about dragon spells are you asking about.
Dragons are not physically real. those who work with Dragons and Dragon Magick see them as spirits. Dragons are astral beings who can help with spells much like calling on an angel or demon. this doesn't mean these spells can contradict nature however, it just means while some call to Aphrodite for help with love, a Dragon Mage would ask a Fire Elemental Dragon instead. you cannot control, create, or become a dragon, but you can call on them if you need help with love, luck, wealth, protection, or any other type of working spell [just be careful with your wording as Dragons take things literally and be respectful] Dragons can also tell when something is a waste of their time so you might get ignored if they feel you aren't ready to work with them yet, or ask for something that doesn't really require magick [like help me find my lost shoe]