I just did a screen share on discord and took someone through a tutorial of ALL MY TRICKS. Some gifs are easier than others to smallerize.
Let me know if this makes sense.
CROPING STAGE 1. At ezgif.com, start at the "crop" tab at the top. 2. Upload or paste in the URL of the gif in question. 3. Select the square check box and crop the gif you want. 4. IMPORTANT: "crop with" drop down, always use gifsicle. (You can experiment with the others but gifsicle always gets the better quality and smaller size gif.) 5. Click the crop image button!
RESIZE THAT DUDE 1. You now have a square gif that is probably bigger than 100x100 2. Select the resize icon that is under that new gif image. 3. Change the width or height to 100 and 4. IMPORTANT: use gifsicle again for the resize method because it'll give you a smaller image size. 5. Resize that image.
I know, I know, those are easy, but using the IMPORTANT steps will often give you something quite a bit smaller to work with, so make sure you use gifcicle for the methods...