KAOz, you need more light, the light position isn't optimal, more resolution (meaning a better camera), a more neutral background (like white or whatever), maybe longer exposure; and you can tweak color distribution, contrast and stuff in Photoshop or Gimp, which is totally legit.
Edit: Also, make sure focus is perfect.
The face you're making is fine, the hair is dynamic, necklace is debatable yet not murder, but you could definitely pick a shirt with a different color. I don't even know what color it is.
It's not perfect, but you're not a professional, so don't dwell on it. You can improve things a lot by yourself though, definitely.