I don't follow your second sentence about the voltage reading as soon as you connect the battery ground. What voltage are you reading and where are the meter connections.
The 14.5 volts is the correct charging output for the alternator.
Your connections appear to be correct as the following diagram shows.
Here is how I do it for a much cleaner look and it eliminates the external regulator and the wiring mess. You can still use the white and blue wires
to extend the brown and reds if you need to.
Notice the two small wires on the diagram (black and black/white stripe.) These are the battery gauge wires and they should have a small four amp fuse in each wire to protect the gauge in the dash.
Your gauge doesn't appear to move. It should move left when the engine is off and the lights or heater fan are on or any other amperage draw. It should read just to the right of center when the engine is running and the alternator is charging. It may read farther to the right if there is a low battery or a large draw on the system.