I use Filterstorm Pro on my iPad Mini. It's just like Photoshop, has all the basic functions of cropping, levels, curves, dodge and burn.
They come in two versions — $3.99 and $14.99. When I first got it, they only have the Pro version so I am not sure about the other one but you can check out the differences here:
http://filterstorm.com/fs4/fspro-vs-fsIt allows you to edit IPTC fields and export it to the size and dimension you need. You can even upload to a FTP server directly from the app.
Anyone have any other recommendations?