how much memory should i buy on an iphone 5

Those 3 are the big memory uses. All my friends who had 32 GB iPhones previously decided to buy the 64 GB iPhone 5. It is a personal decision, but iPhones cannot have memory added, so what you buy is what you get. Good luck.

The short answer is to buy as much as you can afford. The iPhone memory is not expandable, so you get what you purchase. Since you tend to collect apps and music along the way, it can make a big difference having the extra space. That said, I have 4,786 songs on mine, and it fills 24.4GB of my 64GB phone. So, with 500 songs, you're not in danger of bumping against the memory on the 32GB if you don't add a lot of television shows, movies, or podcasts to that. Apps generally (read, "GENERALLY") don't take a tremendous amount of space, with the notable exception being navigation apps that store local maps (like Navigon) which can take about 2GB or so on their own.

I looked at it this way. The minimum available is 16gb for $199. For $100 more you could get a 32gb model. I was trading in a 32gb iPhone 4, so the minimum I would consider was the 32gb. But for $100 more, I would get double that. Better to have too much than not enough, since it has to last for 2 years with the contract.

Good Luck on your decision.