When deciding what iPhone to buy so you end up with the right amount of storage capacity, you can get the bare-bones $16GB model, or you can end up with an upgraded 64GB, or 128GB model, which are probably your best bets with the new video cameras capable of recording at 4K quality.
That's not to say you won't pay a pretty penny though; moving up to 64GB from 16GB is $100 more, and moving up to 128GB from 16GB is a staggering $200 more. But if paying that much more for a storage upgrade is going to be too much for you, then you'll be happy to know there are cheaper alternatives, so long as visiting Shenzhen, China is on your bucket list for the near future.