Theo's daughter has $500 and wants a computer for school. Leo says he likes Chromebooks, and $500 will get her quite a bit. It's all web based, so if that's her main focus, it's a great choice. It does have 16GB storage for offline access.
There are other choices as well, like the Microsoft Surface 3 Tablet, which comes with Windows 8. The HP Stream is about $300. The Dell Inspiron 15" Touchscreen is about $375. Just remember, that anything under $500 is going to have compromises in hardware.