Everything needs to be earthed, normally all the pots share earth via links soldered directly to the back of the pots. In the pitbull diagram they are purple lines, which are then in turn connected to the 'sleeve' of the output jack and also to the body of the switch. If things are not earthed properly the circuit won't complete properly, so you'll either get nothing or buzzing.

It's a really good idea to read up on guitar electronics, its actually not very complicated and the better you understand how the signal flows, the easier it is to diagnose.

The signal from the pickups goes to the RH tang (with all the tangs on the pot facing up) and then out from the middle tang to the switch. Then from the switch to the output jack. The RH tang also bridges to the tone pots, so when you turn the tone pots you alter the amount of signal sent to ground there via the capacitor, which in turns alters the sound. With the Tone pots on 10 no signal is bled. Same with volume, With it on 10, essentially the signal is flowing unaltered through the pot. As you turn the knob you increase resistance and lower the volume.

You'll note the the left hand tang needs to be bent up and soldered to the back of the pot as well so that the resistance strip in the pot is earthed.

All that said, you might just have to pull it all out and post some pictures so we can spot any problems.