My first few attempts at creating a video in Premiere Pro then adding them to my phone for Instagram I found that the format would not match. So, if you are looking for what works, here is what works for me.
H.264 codec / MP4
Sample Rate – 44100 kHz mono
Bitrate – 128 kbps
3 to 60 seconds
Composition Size:
maximum width 1080 by 608
Frame Rate:
29.97 frames per second
 3,500kbps to 5,500kbps


Aim to keep it under  50MB.