Import everything and then remove all the redundant frames. You can't just cut out every other frame with anime. I use a time of 0.04 for each frame so of course if two frames are identical and I remove one I make the one remaining frame 0.08.
Then I look at a scene where the animation between frames doesn't change too much i.e. camera pan. So take when Futaba is jumping up with the bat. I removed every other frame because Futaba herself changed every two frames and a funky background like that doesn't lose much when chopped.
Then I used to erase the parts of the scene that hadn't changed from the previous scene such as the other kids in the first part of that gif. This took ages. Then I worked out there is a much easier way of doing it as I posted earlier:
Then of course it's a matter of playing with the colours and dithering. If dropping the colour count affects the quality too much I'll shrink the image dimensions. I always start at 500 width for anime scene gifs.
If anyone else has some tips please share them.