Which export for display a loop illustration on Facebook?
Giphs have the problem that they are heavily compressed most of the time. Uploading the file to Giphy or facebook might additionally re-format the file and compress it even more, as does youtube or vimeo with their files aswell. You might want to try and increase the resolution of your composition and upscaling everything. In your viewer, not a lot will change, but with a higher resolution, the gif should be a bit more readable at last. Also, try to make Text as large as possible, without blowing it out of proportion.

If none of that helps, you might want to look into other containers and formats that support high web-compression and looping, such as webm.