As others have said, get as much storage as you can afford. I'm guessing because your're buying the ipad 2 16 gb that your 're buying a new one at $399.00. In March '12 we were going to buy the "new" ipad for my husband. After a lot of research, we decided to get the ipad 2 32 gb. We couldn't find new ones anywhere, so for the first time we bought refurb, and because it was $499.00, we went to 64 gb, and are happy we did. (The refurbed ipad 2 with 32 gb is $399.00, but it's been out for a while. (Things come on and off the refurb store, so you have to check often.)
We ordered the ipad and had in about six days at the most. My younger son decided he wanted one, and it took about six weeks before the 64 gb came up in the refurb store.
The refurbed ipads come with a brand new front and back, a brand new battery, and a full one year warranty. My son needed the 64 gb for college, and my husband doesn't really need it all yet, but it's good to know it's there.
Note that the ipad, when new, will have already used up space that is necessary for it to work. So you won't start with 16 gb. Also, as my husband has been learning about all he can do on it, he uses more space.
You cannot increase or upgrade the storage on your ipad, and there are a couple of external hard drives where you can store music, movies, etc., but they cost as much and more than the extra $100.00 to get the 64 gb.
Hope this helps and enjoy your ipad when you get it.