During the point where you can hit the main bar, you use the seal of deflection to bring it down. You get a lot more money then you spend on potions on the bar. For instence, I get 41m a item.
Step one: Clear the blue bar by assassinating and using your troops. Once you do that... Step two: Use the Seal of Deflection defense potion to lower the red bar. I believe you make like 35ish mil an item. Once this bar is at 25%... Step 3: Same as step one, but you need to do around 3 times more damage to get rid of the bar. Then... Step four: Same as step two, but only from 25%-0%, then you win! Hope that helps
First assaination takes off the most skeletal appirations but use attack if you are going for fast cash. You will assassinate the same amount of troops every hit for a full unload but only on Assassaination then if you can make sure you do the item bar because in my experience it will at least quadruple your bonus at the end. Hope this helps