Anatomy and art theory is considered the most important thing in art in my opinion. Often, people don't know there is such thing as "art theory" and ignores it. Many people believe just practicing will make you become a great artist. But I'm afraid that's not true, you'll never get anywhere without reading up.
What I can see in this picture:
- The face is not lined up with the angle of the head
- The upper part of the left arm is longer than the upper part of the right arm
- The dragon's lower jaw is longer than it should be
- The thisckness of the dragons neck is not consistant throughout
- If his hair is like that, a breeze should be blowing, right? His coat is not reacting to the wind
- Not the right type of teeth are in that dragon's mouth. All of them are canines, make sure you have canines, molars and incisors in it's mouth.
Your rendering skills are a bit... weak. Don't just scribble in the colours, gently shade them in, making each stroke sit next to the other, or follow the shapes with your pencil and create a sense of 3d-ness.