When you have equipments that killed God King Level 150, you can defeat the three Hidden enemies that are on three doors on the cave or whatever it is, but you need to buy The Infinity Blade to open the three doors. When you defeat the Gortoel (one of the Hidden enemies), you will receive a Dragoor Bone (a shield). When you defeated the Kuero (another hidden enemy), you will receive the Dragoor Scale(a ring). When you defeated the Ealoseum (another hidden enemy), you will receive the Dragoor Blade (a sword). When you have found all three Dragoor equipments, restart to Bloodline 1 and defeat again the three Hidden enemies then you will receive another Dragoor Scale, Dragoor Blade and Dragoor Bone. You will now have 2 Dragoor Scales, 2 Dragoor Blades and 2 Dragoor Bones. After that, sell 1 Dragoor Scale, 1 Dragoor Blade, 1 Dragoor Bone or 2 Dragoor Scales, 2 Dragoor Blades and 2 Dragoor Bones then you will have a hundred thousand coins or a million coins (plus you will unlock a big secret door with a big stone with designs that leads to a secret lair then you will battle with a robot called Zero Mech and a mere mortal and I don't know what is his name, but it is the one that you used in the first bloodline and I think it is the father of the character you are using now).
Use the time between battle sequences where you are able to assess your situation to increase your stats and look for loot that is laying around as this will earn you money and additional potions that can help you with health.
Always try and use items that have not been mastered as this will earn you XP and Skill points making your character stronger. Once an item has been mastered and maxed out for XP switch it out by either selecting a different item in your inventory or by buying a different item.
First, get to Bloodline 6 through 10 or higher and equip something with gold++. Then, defeat as many enemies as you can. Each enemy you beat should get you thousands of gold. If you want to do this again on the same Bloodline, let The Dark Knight beat you and select "Save and Restart Castle".