Just get some 10 or maybe 12 awg (10 awg could be over kill
) best type is Teflon coated, I don't recall the other type that is normally talked about. Don't use the rubber coated wire (melts easy), if you get short or over heat it the whole hardness and maybe your rig will go up in flames.
To give you a example if you were to use 16 gauge with two 100w lights, 16 gauge max current is 22 amp. Watts = volts * amp, so 12* 22 = 264 watts. That wire is just on edge and it would work but no safety margin, plus I am not taking in to account all the other connections in your lighting system, thus lowering the total wattage handing of the harness. Jump up two gauge's to 12 and you get a max current of 41 amps or 492 watts. Since the wire to the lights is the longest run you want to double or maybe triple the gauge. This way you won't see any dimming going on. Also use some dielectric grease on the mechanical connections will help stop any connection from corroding. If you want a really good system solder everything, only down side is no trail repairs.
http://www.powerstream.com/Wire_Size.htmhttp://www.offroadtb.com/articles/tech- ... -diagrams/