Better measure the bearing clearances with some Plastigage!Did you put in a new pumpor rebuild the old one. Did you check the relief valve and spring? Check to make sure that there is no leak in the oil pick up tube that"s not allowing the pump to pick up oil.
The oil line to the gauge does not need to be primed with oil. Make sure the oil line isn"t clogged-blow it out with compressed air. Pull the coil wire out of the tower, remove the oil line at the block,pull the spark plugs and crank the engine over to see if you have a bunch of oil come out. Run a wire into the block to see if some swarf is clogging it. Crank again,If you don"t it"s "Houston, we have a problem" time.
The gauge usualy works or it doesn"t. It may not be accurate, but it should show pressure unless it"s really damaged. Blow some compressed air into it an see if it moves. If it does, it"s working(again it may not be accurate).