I second the Pokemon trainer suggestion. Some of the ones in the games/manga/anime have really cute outfits, or you could even design your own character. Also, any kind of school uniform might be good (Haruhi, Azumanga Daioh, etc). It might seem kind of boring but that kind of cosplay is really good for beginners and a great way to build sewing skills.
Completed Cosplays: Misty (Pokemon Indigo League), Yuki Nagato (The Melancholy of Haruhi Suzumiya), Rico (Gunslinger Girl), Yellow (Pokemon Special/Adventures), Fem!Fifth Doctor (Doctor Who)
In-Progress: Aigis (Persona 3)
Future: Alice Malvin (Pumpkin Scissors)
Future Cons: Anime Nebraskon 2013