First, you must make it to Bloodline 3 and restart Bloodline 1. You will then have to battle the Dark Knight in the final area of the castle. When the game asks you to hold down the shield to block, just tap it once. Keep doing this until you are killed. You will start the game on 'Bloodline -1', unlock a special achievement and get the Dark Armour, the best in the game.
One of the quickest ways to get gold is to fight the first enemy, and pick up the bag of gold in the next area. Then restart the current bloodline and keep doing this. The first enemy is very easy to defeat so you can very quickly start gaining gold.