You first need to remove all nvidia stuff.
Code:
$ apt-get remove nvidia*
Then, find out which nvidia driver package you need from the Debian repos. Install the correct nvidia driver and it should bring in everything you need. You also need to blacklist the nouveau open-source nvidia driver so it doesn't load.
Then install bumblebee after you're sure you've installed the correct nvidia driver for your gpu. Debian frequently installs the wrong version of the nvidia driver to discourage its use. After that's all done, bumblebee should work.