It would be good to know what "bad quality" is, or examples of what you're talking about. In my opinion you're going to have to take the multiple export approach following a couple of pretty strict guidelines.
1) The clip should be no wider than 1000 pixels.
In order to achieve that for any clips that I know are going to IG; I export from FCPX in 1080p
2) The clip should be no larger than 15MB
In order to achieve that I open the the exported clip in Handbrake and I've created 2 custom picture settings profiles one that exports at 1080x768 and another that exports at 720x480
If you're wondering why not just export from FCPX in the desired size. The answer is because, I've never been able to get the FCPX file size below 15MB.
I will post examples later if you're interested, I'm on my way to the train station.