I'm sorry I've tried to build an AppImage before and it hasn't worked.

On the unstable branch I just created a script to build an AppImage. If you want to try it:

$ git clone https://github.com/mikedilger/gossip

$ cd gossip

Or if you already did that, update with

$ git fetch

Then either way:

$ git checkout unstable

$ cd packaging/appimage

$ ./build-appimage.sh

Let me know if it works

Are you running Debian?