Unlock ALL Regiments:
When you are at the 'Caravan' screen move the cursor over the spare book under the pile on the left and then hold 'Select' and press R1, L1, L2, R2.

Unlock Infinite Magic:
When you are at the 'Caravan' screen move the cursor over the Magic book and hold 'Select' and press Left, Up, Right, Down, L1, R1. When a spell is now cast during a battle no points will be deducted.

Unlock Troops:
When you are at the 'Caravan' screen move the cursor over the Troop Roster and hold 'Select' and press Circle, Triangle, X, Square, Left, Right.