Depending on the gauge you select, it comes with the plug installed in the gauge. So you will have to buy the other end to wire it up. But it should tell you what type mating plug to get. As far as wiring goes, try to buy marine wire because it comes tinned and therefore will help control corrosion better. The gauge size will depend on the amount of current the gauge needs to operate properly AND the distance those wires will run. The longer the run, the bigger the gauge size. But with that said, unless you are installing an amp meter, most all other gauges can use a typical 14 or 12 gauge wire safely without any problems. Wire colors also depend on the gauge and its function. That is if you plan on being wired to standard marine systems. JMHO!