How to save a gif in photoshop with the smallest file size (150kb)

Hi,

So I made an mp4 in aftereffects ( I didn't do this in photoshop because of the effects) and now I have to save it to max. 150KB.

When I save the video in aftereffects (3seconds) it's like 100kb. Than I open it in photoshop and save it for web.. I don't know how but the gif is like 2MB.

I tried to save it with less colour and no dither. 128 colours is the best one. Beneath that it's losing a lot of quality.

I hope someone can help me!!