Haven’t figured out a way to limit to or optimize around a specific file size yet without a second app, but in Photoshop CC 2015, this script allows me to automate>batch videos to gifs at a decent quality at a little less than 1MB/SEC of video:
With a video open, record this script:
1) In the timeline menu (top right of timeline) set timeline frame rate to 10fps
2) convert frames>flatten frames into clips
3) convert frames>make frames from clips
4) set the work area forward to start at your first frame
5) file>export>save for web (legacy) and choose GIF, 640×360, 128 colors, looping forever
Hope this helps someone else
If there’s a will there’s a way