The first thing that comes to mind is, do you have the correct repos in your system? One always needs them to install what is needed.
There are some apps that can be readily installed from the default repos. Then there are others that need certain (non-free, multimedia) repos in your /etc/apt/sources.list to get.
Try searching for the appropriate repos to add to your /etc/apt/sources.list for your Debian branch. Then try installing the apps you want.
As far as source packages; some love them, I don't. If I can't apt-get install (whatever), I don't even mess with them. But that's my opinion. Grrr, I hate tarballs!