As soon as an enemy troop responds, turn around and flee. Lead the pursuing forces into the mouth of the V you've created and watch how quickly they die. There's really no comparison to the well-set trap, but once you develop your game to the point of building Towers and Wizards, be sure to crank out as many Wizards as you can afford. Rather than sending Raiders up into enemy territory, Demons and Spiders serve much better. Once you've four or five Wizards sitting behind your defensive line, you can rotate among them and send Demon after Demon into your enemy's territory.
Spiders are great for misdirecting enemy catapult fire as well.
Cast it on a Water Elemental or a Knight and send them behind enemy lines into the midst of the Orcs' Peons. Before the Orc player can respond, every Peon they have will be dead. If you cast it on a catapult, you can position it behind enemy lines, directly in range of your opponent's town, and attack from a rear, perhaps even protected, position. By the way, defending against the invisibility spell is a real trick. You need to find that place on the map where you can build a complete wall.