The tactic is as follows:
In the first week, try to deploy Vampires and Liches whenever possible.
If there are no resources, build a Town Hall, recruit Skeletons, and go into battle.
Black Knights, Liches (especially against living creatures, as they attack in an area), Vampire Lords, and, of course, Skeletons are very useful in battle.
Since Skeletons have low speed, I prefer to take the Haste spell.
Sometimes, Phantom Dragons are useful. They may be weak, but they can inflict the Aging effect.