I want to buy iphone for the first time?

I want to buy iphone for the first time.
also i don't want to spend much money on a cellphone… I don't know if i should buy a used one or not…
4s--5(used)---5s(used)
and also i'm afraid to buy a used one and it turn out bad… Since i want to tell my aunt to buy it for me from canada!

Get a 5s or a 5c