Assuming battery gauge means ammeter.......assuming "which wires to use" means "how do I wire the ammeter".......or which harness wire numbers and colors to use?
One side of the ammeter gets battery voltage direct from the battery or bounced off the starter. The other side gets ALL the loads to read. ALL loads includes the alternator, the fuse panel, ignition switch. The ignition turns on some of the fuses. Other fuses are always hot.
The need for the mega fuses is debatable. I do not use them. Sometimes i use a fusible link. The harnesses usually do not support ammeters. They support voltmeters.
You are passing 99.99% of the voltage right thru the ammeter. A small millivoltage is tapped off to measure.
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn
