I am wondoering what guage wire to use for wiring up my controller. I am using a 50V 16A power supply, CNC4PC C11 Multifunction BOB, Gecko G203V Drives going to Kelinginc 906in/Oz Stepper Motors? please any help would be greatly appreciated.
Your wire should be sized according to the amount of current they carry. Obviously, a bigger wire can carry more current. I normally use 16 or 18 Ga. for power wiring (motor leads, AC power leads, DC power leads) and 20 or 22 Ga. for signals (step/dir, limits, etc.)
Here is a chart showing current carrying capability for most common wire sizes.
Its generally good to go a little overkill on the wiring as a fire can be a lot more expensive than the few dollars saved on smaller wire. You also need to make sure everything is properly fused and grounded, shielded, separate power and signal wires, etc. There are some pretty good wiring diagrams floating around here which should give you a good start.