I've had my first rx7 for about 2 months now and I have a question about acceptable oil pressure through the stock gauge.
When cold the gauge will rise to almost the top and slowly sink,
While under any kind of load the oil pressure rises to numbers that are acceptable.
However, when the car is warm and at idle the gauge reads barely over 0, I just changed the oil (10w30) and received the same results

 

Mine does something similar, except it doesnt go any higher than "60" whatever that is. And at idle it goes back to around 0 until i step on the throttle and then it slowly goes up

 

The connection between the wiring connector and oil pressure sender is known to be problematic. They are pretty easy to get to, so cleaning them and re-connecting them usually gets it working for a time. They do go bad, but usually it's the wiring connection. Once you get to know your car's behavior, it's a matter of noticing if something is different.

If you are really concerned about the actual number, you'll need to install an aftermarket gauge and sender.

PS. The oil pump is mechanically driven, so the pressure is supposed to increase with engine speed.