Default Game Window Size To Take While Making Games

I am planning to make a game for mobiles and tablets, I wanted to know what would be the default resolution that I should set for my game so that it covers all or most of the devices out there.
I read an article someplace that says we should design the game for lowest resolution like 480 x 360 and then scale it according to devicePixelRatio for the target device, Is this the right approach because according to me it will be good only for devices that have 3:2 resolution but what about other 16:9, 16:10 etc
So What should be the base resolution I design my game so that it gets scaled to all mobiles and tablets