Donia, believe me when I say that practicing DOES help and it will help you. Also having people telling you where you're going wrong in the picyutres will help. They can see things that you may not. I started of copying as well and then moved onto real pictures...in fact this a picture that I did when I frist started drawing;

Aweful isn't it. So you can believe me when I tell you that I'm not naturally good at art, it did take lt of practice, and I'm still not happy most of my art.
As to bok, well I'm afraid that I can only recommand manga drawing books.