Quick note: this isn’t the “classic” green tunic from a previous The Legend of Zelda title, but it’s close.
In the video above Arekkz show you how to acquire the green tunic made specifically for The Legend of Zelda: Breath of the Wild.
If you don’t have an amiibo, this outfit will be as close as you can get to the classic tunic worn by Link in previous titles. The pieces are: Cap of the Wild, Tunic of the Wild and Trousers of the Wild.
This costume, again, was created for the game and in order to obtain it you need to complete all 120 Shrines and you then get one final quest.
If you want to know which The Legend of Zelda amiibo drop which outfits, here is a quick guide on that. To find out which amiibo work with the game, and the goodies they offer, here’s a guide for that as well.
Hope this helps you out.