The CX3 is based on the 2, so al lot of similarities with that model.
The entertainmentsystem is identical for all the Mazda's, so all the info is usefull.
For updating the navigation, if you have the sd card, is free the first three years. Your VIN number (chassisnummer) is coupled to the card, and the time starts running when the vehicle is past the 100 km mark.
Make an account and download the Mazda Toolbox for updates. My previous owner did not know this, the maps were four years old. My car is from 2014.
For the update of the audio, the front and rear speakers and adapters of your CX3 are identical to the rear door speakers of the 3, 6 and CX5, and smaller then the fronts of these models, but an 165mm speaker will fit just fine.
There are two updates every year. After three years you have the option to buy an single update for €120,- or a three year update for €180,-
I bought the three year option.
A lot of people search for alternatives, both illegal or with the phone and apps like Google or Waze, but I think that when you have a car with build in system, you should update the system and use it. When you calculate the cost as maintenance over three years, there are a lot of other costs that run much higher. In my last 3 from 2005 I had to replace the condensor for the AC system twice in five years and set me back more than €500,- each time. It's nice that Mazda gives the three year free option, I think it's good service.