At the beginning of 3rd level your flying speed is increase by 10ft.

At the beginning of 6th level your flying speed is increased by 20ft. Your breath weapon's range doubles.

At the beginning of 10th level you draconic ancestry resistant trait becomes an immunity and your breath attack's damage dice go from d6's to d8's

At the beginning of 15th level you start gaining the traits of an actual dragon, you gain a wing attack. You beats your wings. Each creature within 10 ft. of you must succeed on a DC 16 Dex saving throw or take 2d6 + 8 bludgeoning damage and be knocked prone. When you use this attack you can only fly half your normal flying speed.

At 20th level you become a full fledged dragon of your type.

You draconic scales on your wings are especially tough and can be used as a shield. you gain an extra +2 AC

You don't have hands so you can't really use normal weaponry, armor, or shields. Your body is as strong as any armor and you can hit as hard as any weapon when you put your mind to it. 

You gain a bite attack - 2d6 + proficiency piercing damage

You gain a body ram - 2d8 + proficiency bludgeoning damage

You gain a Tail swipe - 1d10 + proficiency slashing damage. Your tail has 10ft reach and can hit up to 2 creatures side by side.

Your body is covered in naturally tough scales, your AC 10 + your STR and CON modifiers 

You can see in the darkness in shades of grey up to 60ft

You don't need to sleep, you need at least 4 hours of meditation in order to benefit from a long rest.

Do to your size and weight your carrying capacity is very high, but you are also really difficult to hide. You have disadvantage on stealth checks but can carry a much heavier load

You can have a saddle fitted to you, allowing for 2 medium sized or smaller riders.

Due to being an unnatural adventurer you can't actually cast the spells normal ones commonly cast. if a spell requires a M, you cannot cast it. if the spell only requires an emblem or symbol to cast you may do so. Not that a dragon would need magic, right?

Your Strength score increases by 2, and your Constitution score increases by 2.

Young dragonkin grow quickly. They walk hours after hatching, attain the size and development of a 10-year-old human child by the age of 2 and reach adulthood by 10. They live to be around 800.

Dragonkin tend to extremes, making a conscious choice for one side or the other in the cosmic war between good and evil (represented by Bahamut and Tiamat, respectively). Most dragonkin are good, but those who side with Tiamat can be terrible villains.

Dragonkin are taller and heavier than dragonborn, standing well over 10 feet tall and averaging almost 550 pounds. Your size is Large.

Your base walking speed is 30 feet.

You have draconic ancestry. Choose one type of dragon from the Draconic Ancestry table. Your breath weapon and damage resistance are determined by the dragon type, as shown in the table.

Draconic Ancestry

You can use your action to exhale destructive energy. Your draconic ancestry determines the size, shape, and damage type of the exhalation. When you use your breath weapon, each creature in the area of the exhalation must make a saving throw, the type of which is determined by your draconic ancestry. The DC for this saving throw equals 8 + your Constitution modifier + your proficiency bonus. A creature takes 2d6 damage on a failed save, and half as much damage on a successful one. The damage increases to 3d6 at 6th level, 4d6 at 11th level, and 5d6 at 16th level. After you use your breath weapon, you can’t use it again until you complete a short or long rest.

You have resistance to the damage type associated with your draconic ancestry.

You can read and telepathically speak Common and Draconic. Draconic is thought to be one of the oldest languages and is often used in the study of magic. The language sounds harsh to most other creatures and includes numerous hard consonants and sibilants. You can telepathically speak to those you directly look at.