Her particular image's DPI is at 72, but there is no need to adjust the DPI when dealing with animated .gifs. I don't reduce colors unless there's nothing else I can do to bring the file size under the 39kb limit. The original file has 45 layers and animation frames which is WAY too many for this animated .gif. I reduce the number of layers/frames first, then work on the reduction type, loss, colors, etc.