Which castle is the most advantageous to play as?

Here's a strategy for you: Week 1: Build creature dwellings; without them, you're nothing. Gather all resources, build dwellings up to level 5-6 creatures. Simultaneously, with your second hero on the map, collect resources, and also capture a lumber mill and a mine. Week 2: Recruit creatures and head to the dungeons (or you can build a ship at the shipyard and go capture abandoned ships). While doing this, kill all neutral creatures, and on day 2, build a Mage Guild up to level 3. Week 3: Recruit creatures and go capture neutral Castles (they will be useful). If an enemy is stationed in a Castle, bypass it (but if the defense is very weak or non-existent, then it's worth capturing). In these Castles, also build various structures. Week 4: The enemy might attack you now, for example, by capturing a Castle or a lumber mill. Recapture everything they take. If they are about to capture your "capital" (the Castle you started the game with), delay them, try to kill them. If they are 2 turns away from your Castle, and you are 3 turns away, hire heroes in the tavern, combine your armies, and wait. If possible, recruit creatures in the Castle. After that, fight them, capture their lands, and so on. Good luck! :-)