The Citadel is a pretty good castle; its advantages include a low unit cost and good growth rate. This city is more suitable for a quick victory because development here proceeds almost without problems. Its disadvantages include weak magic; otherwise, I don't see anything particularly noteworthy. The heroes here are quite good – Battle Mages and Barbarians. Personally, I usually start with Dessa, as she has Logistics, which is highly valued in the early game. Then, during the first week, I try to upgrade the Griffins, and after that, I follow a well-established strategy, building either Cyclops or Ogres and heading into battle!