Gifts depends on the girl. If she likes art, buy her a sketchpad or a coloring book-----once it's colored, paste pictures or quotes there. ;)
If she likes movies, give her a link to a website that provides all the movies she likes, or a movie marathon, a date at the cinema, or plan a sleepover, use a projector, pile some blankets, make a tent, some snacks, and there you'll have a home-made cinema. ;)
If she's sporty, give her some new pair of sport shoes, an armband, or some new jog pants, a tumbler. She'll appreciate that.
If she's girly-girly, make sure to have a lot of money to treat her during shopping. Gawd. xD
If she's plain, simple, bookworm-ish, an e-book would do, or a new book that's a best-seller. I have a few recommendations here if you're interested.
And the best of all presents are the ones YOU need to think of. Pay attention to her little things. Like she doesn't like fluffy pillows or armbands, if he likes to keep her hair up or tied in a ponytail, or she likes teas or coffee, listening to music or a composer, a writer or a reader, a taekwando player or a runner, or is she a selfie-addict and Facebook fanatic..... There are many gifts for those alone. :) Hope this gave you some ideas. :)