How many GB do I need? (iPhone 5)?

I'm a teen, so I'm not going to use my phone for business or something. I just think that I'll use my iPhone 5 to download a few fun games, a ton of music, videos and loads of pictures. How many GB do I need? I have an iPod (32 gig) and I've downloaded so much, but I've only used up 8 GB which is good. My sister has a 8 GB iPod, and it ran out of space when she didn't have a lot of things in it, and since 16 GB for an iPhone is only twice the amount, I'm afraid it's not enough space. Is it?

You need 500 GB