To test it accurately you need to hook up a real gauge, one with numbers. If you just want to check the accuracy of the gauge set you have, just buy a $20 el cheapo, hook it up, and compare, then unhook it. Personally, I would install at least an aftermarket oil pressure and water temp gauge.
The rule of thumb for oil pressure is 10 psi of pressure for every 1,000 rpm of engine speed. I get about 35 psi at idle, and up to 60 on the freeway.
A ticking lifter can be a symptom of not enough oil pressure. There can be numerous causes of this, but my first question would be, how much carbon deposit is in your engine? have you popped off a valve cover? How long does it take for your oil to turn black?