Could we have more information please? Detail your workflow a bit more clearly. Are you trying to make a gif file or import a gif file?
To render an animated GIF and your composition to the render cue, choose the lossless with alpha preset from the output module templates, render your movie, open the movie in Photoshop and choose save for web has an animated GIF and you will get the best results possible. You can clean up the Photoshop file to remove duplicate frames, I just the timing of each frame, and make your final file smaller and more efficient.
Animated GIFs dated in After Effects are very poor quality. Creating them in Photoshop from a movie is the best way to go.