Gauge is how much current you can push through without losses.
There are hundreds of charts listing how much current is safe to transfer without beeing a fire hazard. There is also ohm per meter/feet tables.
One such list
Resistance (Ohm) in cables is just loss during transfer.
Coaxial (as in antenna cable) and other signal cables (DMX cable for example), you do not want to use that for speakers. It is like putting a resistor in line (will bring volume way down in the best case). Avoid this.
The usual speaker wire used for PA systems is 2.5mm² (~ 13AWG) up to 6mm² (~9AWG) for long lengths.