Instagram 'quality' secrets

I know this issue has been talked over quite a bit, but I haven't seen anything to recent on it. Has anyone cracked the secret of how some people seem to be able to upload good quality vector style / flat colour images to Instagram?

Have recently uploaded some flat colour raster images that originated in Illustrator, but where imported and then exported out of Photoshop having done some work on them. The thumbnails and the finished artwork look awful once uploaded, and across multiple devices too. They looked great when they came out of Photoshop, no issues there. Looking across other designers artwork, some of them seem to have cracked the secret to keeping the quality in their Instagram uploads, does anyone here have any tips or hints? 

I have tried .jpg all the .png variations, lots of different sizes and depths, have added noise etc. and had almost no improvement in quality (all sRGB). I've also recently uploaded an animated version from AE and had similar issues with the thumb and the vid too.

I know Instagram compresses everything, but some people seem to have worked around this, and I need to know their secret! Feel like I'm probably doing something wrong somewhere. Any help would be great.