The easiest way to grind for money is to send your runners for diamonds, malachite ore and maybe plants for the most expensive potion you can make. see
Runners and Tower ?The bunker is the place on the side of the mountain with the anti-dragon shields around it, until you disabled them and the barrier blocking off the test of the fjords. After climbing up the ladder and fighting two black ring members (lord and lady something) the two upstairs will offer their surrender, and trade with you if you accept. You can not get to dragon cliff castle without disabling the barrier from inside the bunker.
The zeppelin quest requires all of the parts to complete, but just one of each type will get one zeppelin working, and allow you to enter Aleroth.
Dragon Knight Saga FAQ/Guide
