Cannot install anything through Terminal - apt-get -f install

I get this when ever i try and install anything with th Terminal:

    You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
 gimp : Depends: libgimp2.0 (<= 2.6.12-z) but 2.8.0-1ubuntu0ppa3~precise is to be installed
        Depends: gimp-data (<= 2.6.12-z) but 2.8.0-1ubuntu0ppa3~precise is to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).

I added myself to the root group in the grub recovery mode. Then did sudo apt-get -f install and got this:

Errors were encountered while processing:
 /var/cache/apt/archives/gimp_2.8.0-1ubuntu0ppa3~precise_amd64.deb

E: Sub-process /usr/bin/dpkg returned an error code (1)

Okay, from what I can tell, your problem is that you've added a PPA to try and upgrade to the latest version of GIMP, and it hasn't worked out. I think the best option for now is to remove the PPA so you can get back your ability to install software.

Open Update Manager and hit Settings. This will bring you to the Software Sources manager, which you can read more about here. Go to the "Other Software" tab and untick any PPA's you added related to GIMP.

Then open a terminal, and type these commands one at a time (you may have to run the third command before sudo apt-get remove gimp if it fails):

sudo apt-get update
sudo apt-get remove gimp
sudo apt-get -f
sudo apt-get upgrade

GIMP will be uninstalled, but it should get your system working again. You should also be able to reinstall the default version of GIMP from the repositories.

Try this:

sudo apt-get build-dep <yourapp>