Been is used when someone has been to a place and he has travelled there and returned,


For example:

Candy : Where have you been?.
Tony : I've been in the City for two days.

GONE is used when someone is till there or at a place or on the way there.

For example:

Candy : Good Morning, Could I speak to Mr.Ali? 
Tony : He's gone to Berlin
Candy : I'll call back later.