If you decide to implement optimizations beyond imagemagick's ones, you might want to consider other tools than Gifsicle:

- lossygif for small size, based on gifsicle, https://kornel.ski/lossygif

- Gifski for high quality, based on pngquant, (https://gif.ski/)

Both are made by Kornel Lesiński. Lossygif is actually result of a pull request being ignored by gifsicle maintainer(s) for years – more details in a recent HN thread: https://news.ycombinator.com/item?id=16573627.