What is the best aspect ratio for a gif image?

I'm trying to make a gif animation from a video using GIMP software. How do you get to change aspect ratio too?What is the best aspect ratio for a gif image?You go to Image %26gt; Scale Image. There isn't an %26quot;aspect ratio%26quot; setting in Gimp, but when you scale your image be sure that the chain link next to the width and height isn't %26quot;broken.%26quot; That way when you scale your image it will scale proportionality.