Q: If I'm a writer, how many gb should I be using?

It rather depends if you write birthday cards or series of novels. Here are some clues:  how many ebooks can a 16GB iPad hold

I'd recommend 32gig at a minium if you can afford it.  Apple is always expanding the "firmware", so you do not get 16gig. I've kind of given up erasing things.

16GB vs 32GB vs 64GB: Which new iPad storage capacity should you get?

http://www.imore.com/2012/03/08/16gb-32gb-64gb-ipad-capacity/

How much content will fit on my iPod or iPhone?

http://support.apple.com/kb/HT1867

How Much iPad Memory Do You Need?

http://ipad.about.com/od/iPad-Tutorials/a/How-Much-iPad-Memory-Do-You-Need.htm

 Cheers, Tom