Staying within FCPX, you can only 'gather up and copy media' which isn't ideal. At the recent Faster Together stage at NAB, Chris Steele from Marquis Broadcast demonstrated Worx4 X that copies and trims media saving a lot of disk space.
If you're a regular reader of FCP.co, then you've likely heard about Worx4 X from Marquis Broadcast. For years, Final Cut Pro X users have asked for a media management tool similar to the one found in Final Cut Pro 7. In many circumstances, the "Consolidate" command in FCPX is sufficient for managing media. However, sometimes you need to trim clips to conserve on hard drive space when sending projects to outside vendors. That's where Worx4 X comes in.
In this presentation, Chris Steele from Marquis Broadcast demonstrates how to use Worx4 X in less than 5 minutes.
Editor: As I get a name check in the video, I'd like to add some precise numbers. A recent hour long show I edited was media managed using Worx4 X. The original amount of files added up to 1.2TB! Running the project XML through Worx4 X ended up with the total new trimmed media at 62 GB- quite a saving. The app even found clips that were buried in compound clips, in compound clips.