Looking for help building my first light

This is my first post but Ive been lurking for a while reading.
I want to build and mod my first light. Im thinking about buying a flashlight kit with most of the components so Ill only need to do minor modifications.
I asked on another forum but they are not exactly helpful. You guys seem like a better group of people.

Im thinking this case/body
op-quality OEM E2 HAIII 1x26650 CREE XM-L T6 Flashlight Host kit
http://www.cnqualitygoods.com/goods.php?id=1675

With this led Loading...

Can you guys recommend a circuit driver and which type of batteries are best (that I can find on this site.)
Id like to find batteries I can recharge if possible.

I was also thinking about an extension. This will allow more batteries and so more power or longer life correct?
Loading... extension

Thanks in advance