If you have the PCB, you will need:
* some wires (just search Ebay for JAMMA harness)
* buttons and joysticks
* a 15kHz monitor (an ordinary TV can be used)
* power supply (+5V, +12V and sometimes you also need -5V, once again Ebay is your friend)
* 8Ohm speaker(s)
The rest is optional like coin door, wood, paint, t-mold and all that other stuff that makes a great cabinet.