To take control of the sort order of your photos on the iPad you need to get a third party app like Photo Manager Pro. These apps maintain their own database of photos, have their own import/export options (though they can also import/export from/to the Photos app), and vary widely in what options you have.
I mentioned Photo Manger Pro because it is popular, but there are many apps with lots of variety in features. Research is in order. Make sure you get one that does what you want the way you want.
Photos is a very basic photo manager; mostly a storage place for stuff you take on your iPad, plus a quick and dirty album sync thrugh iTunes, plus a few other features that don't always make sense.