when exporting a project from Ae to Me, when saved as a gif it gets grainy, how to fix?
a) for better result and better control of your gif you should use Ps as final export tool, or use f.eg. script like GifGun in AE
b) gif is old and quite restricted format (8bit, 256 colors on frame etc.) so if you wish to make full color crisp file - gif is notthe way to go. 256 colors per frame is not enough to do that so that is probably the reason that your GIFs are grainy.
Yes. 256 colors is to little to show full color image. Here comparision on left heavly compressed jpg and on the right gif
jpg can save 16 milion of colors GIF only 256.
So what you are describing as grainy picture is probably that.
As for transparency about wchich you are asking in PS topic - GIF can't save alpha channel (transparency) and never did so if you wish to save transparency - gif is not format that you should use.