I know lots of girls. I know girls with blond hair, brown hair, red hair. I know tall girls, and short girls. Most of them are gorgeous, because God has made them that way. Even without makeup, girls can be and are pretty.
However, no matter how much make up you use, or natural beauty you've been blessed with, nothing can disguise an ugly personality.
If you treat people badly, they won't think you're pretty. If you never smile, people won't see a beautiful face, only an unhappy and bitter person. If you don't shine the light of Christ, then you won't be beautiful to God, and that's especially important.
One thing we all need to improve on, no matter how old we are, is inner beauty. Especially as Christians, we need to be beautiful on the inside, where it matters. In 1 Peter 3:4 it says, "but let your adorning be the hidden person of the heart with the imperishable beauty of a gentle and quiet spirit, which in God's sight is very precious."
Make sure you're beautiful inside before you work on your outer beauty.