I buy all of my games from Gamestop or Wal*Mart. I would order offline, but my mom doesn't trust her info on the internet so she won't let me use her credit card. I also buy from yardsales.
Primarily from the Nintendo eShop, but I sometimes buy games at Amazon, Yodobashi. or AKIBA-HOBBY too.
Amazon.co.jp for online shopping only, AKIBA-HOBBY for physical store shopping only, and Yodobashi is excellent both ways.
I even pre-ordered Taiko no Tatsujin Nintendo Switch Version at Yodobashi, but since I pre-ordered at the physical store, I will have to pick it up there myself.
I only buy games that the official store because I am afraid to buy on the unofficial one because I felt like it wont work and it is so risky I don't want my money to be waste.