The basic problem I think is that 14.04 is too old library wise for versions newer than 3.12 (similar subject covered here). You would need to wait for 16.04, or use 15.10 and the GNOME PPAs to get something easily that would work (15.10 is currently in Beta but due to be released later this month). The LTS releases are supposed to be stable, so aren't always up to date with stuff.
The only place I have been able to vaguely use Gnome 3.18 is in Fedora 23 Beta (which I think is still roughly the same as the official Gnome Next image) - it probably is also available via ArchLinux.
Ubuntu is usually behind on Gnome releases - they have just got most of Gnome 3.14 in 15.04 - and you can get 3.16 with 15.10's Beta. With the 15.10 you probably can use the Gnome Staging PPA to bump the version to 3.18 - it also the same same for 15.04 and 3.16).
Last Updated: 04/10/2015 for those thinking in future "Aren't we on Gnome 5.2 now?"
The basic problem I think is that 14.04 is too old library wise for versions newer than 3.12 (similar subject covered here). You would need to wait for 16.04, or use 15.10 and the GNOME PPAs to get something easily that would work (15.10 is currently in Beta but due to be released later this month). The LTS releases are supposed to be stable, so aren't always up to date with stuff.
The only place I have been able to vaguely use Gnome 3.18 is in Fedora 23 Beta (which I think is still roughly the same as the official Gnome Next image) - it probably is also available via ArchLinux.
Ubuntu is usually behind on Gnome releases - they have just got most of Gnome 3.14 in 15.04 - and you can get 3.16 with 15.10's Beta. With the 15.10 you probably can use the Gnome Staging PPA to bump the version to 3.18 - it also the same same for 15.04 and 3.16).
Last Updated: 04/10/2015 for those thinking in future "Aren't we on Gnome 5.2 now?"