Not wise go 5c as iOS 11 don't support it any more
At least get a 5s
Why is iOS 11 a factor in getting a second phone as spare?
Okay. Not wise in getting 5c then.
It rly depends on what is the purpose of the spare phone.
For my case my spare phone is a iPhone 4s. Can use as personal hotspot for my phone and my wife's phone but slow only. 4s support until iOS 9. But can use grab and uber which is good enuff for me when I'm overseas.
So, rly depends on your purpose. If one day grab and uber stop supporting iOS 9, that means I also have to change my phone.