Look at your FSM. The electrical diagrams show the eight pins and the rest of the circuit. You will see where to attach your 12v power source (and don't forget to ground the cluster). Then with 12v applied you will see which pin to ground (goes to the senders, gas, temp) and that will peg the gauge and tell you it's working.
Unfortunately, I don't have a FSM for the Rallye dash. I do have one on CD for my Duster, but it doesn't include a wiring diagram for the Rallye dash. I have ordered a color wiring diagram specific to the Rallye dash, just waiting for it to arrive.