Well for the first attempt thats not too bad.
Some things I could point out
1. match face and neck colors better, maybe look into some youtube tutorials for coloring, you will see how many colors go into making proper shadows and color transitions.
2. more detail on the hair, hair are never stuck together in one piece like that... well unless you wana immitate someone using a lot of hair gel
3. add more details to the eyes, if you look real close to your own eyes its a LOT more than a single color and a black pupil
Overall around the whole picture focus more on improving the shadows and lineart.