Generating sprite sheets
Roblox doesn't allow users to upload GIF files, so to work around that, you need to convert your GIFs into sprite sheets. You can use https://gabys.xyz/gif_to_sprite to do that.
tip
Try to keep your sheets as square as possible.
tip
Having more than 100 frames in a single sheet will make the GIF very blurred. Split your GIF into multiple sprite sheets to avoid that.