I am going to create a game for the Android using Unity. I would like to know which database to chose for the game. And I would like to know how is it possible to save player info with a connected Google play account. What I mean by this is that I would like the player to be able to play from a phone for a while, achieve something in the game and after that I would like him/her to be able to take another android phone, sign in into a Google play account and got all the earned previously achievements.
The database should be free.
Here seems to be a great tutorial, but I am not sure whether or not it is worth spending time.