When converting video to gif, I always use palettegen, e.g.
ffmpeg -i input.mp4 -filter_complex "fps=15,scale=640:-2:flags=lanczos,split[a][b];[a]palettegen=reserve_transparent=off[p];[b][p]paletteuse=dither=sierra2_4a" -loop 0 output.gif
[1] https://blog.pkh.me/p/21-high-quality-gif-with-ffmpeg.html
Does ffmpeg's gif processing support palette-per-frame yet? Last time I compared them (years ago, maybe not long after that blog post), this was a key benefit of gifski allowing it to get better results for the same filesize in many cases (not all, particularly small images, as the total size of the palette information can be significant).
I use `split[s0][s1];[s0]palettegen=max_colors=64[p];[s1][p]paletteuse=dither=bayer` personally, limiting the number of colors is a great way to transparently (to a certain point, try with different values) improve compression, as is bayer (ordered) dithering which is almost mandatory to not explode output filesizes.
Gifski (https://gif.ski/) might be a good alternative to look to that's gif-pallete aware.
In many cases today “gif” is a misnomer anyway and mp4 is a better choice. Not always, not everywhere supports actual video.
But one case I see often: If you’re making a website with an animated gif that’s actually a .gif file, try it as an mp4 - smaller, smoother, proper colors, can still autoplay fine.