You shouldnt have to gather any directories XPression has an export process specifically for this scenario. Go to the file menu and select "export package". Follow the prompts to complete the process if you have files in your project directories that you are not using but want to keep, select the "unused files in project folders" option during the export.
Once you have exported you will have created a .xpp file or "XPression Project Package" which will then have to be deployed on the new system. You can deploy this package as many times as you want so I would suggest doing a test deploy to make sure you have all of the assets you need.
Cheers
Andrew
#XPression