Exporting a file with performance issue (transparency issue) [Animated GIF]

[zaxiade]

Sprite details

• number of frames: 18
• sprite resolution: 330 x 500
• session duration: 1 hour

Trying to export a high quality pixel file WITH transparency but performance issues occurs, saying its too many pixels being used:
How can i lower the amount of colors (it says i have too many colors and even when i erase most colors or instead take some out it still says too much? Or is there a way to help boost performance for this program it so it can export high quality + transparency?

Trying to find a work around for this that wont destroy the quality of my animated gif or have a background to it.