I just hooked the Christmas gateman up today.
There are 3 terminals on my gateman: common, man, and lights. (lights may be optional). I have mine set so that it operates only when the train is running. Common is connected to the center rail, man is hooked to the outer insulated rail. This should operate the gateman. The light can be connected to a spare terminal on the transformer: find one that doesn't cause the man to buzz. (If you have the CW80 transformer you can get interesting problems, depending on when it was made.) You could connect the light to the other running rail; shorter wires but light varies with train speed.
The crossing gate probably wires up similarly, but only 2 wires?
You can extend the insulated section cheaply by taking the metal bar that joins the outer rails off the underside of the track section. This also lets you make curved insulating sections. Gently pry up the metal tabs holding the bar then fold them down again.
If you want the accessories to operate when the train is stopped, the center rail connection needs to go to an accessory post on the transformer instead.
The expensive solution is the infra-red detector.