^
Progressing to the 3* HoH merely requires playing missions and moving on. The 2* HoH can be beaten with the Cobalt set you're given. Upon completing the last few missions before the 3* HoH, you get 8 Advanced Orbs of Alchemy. Those would otherwise cost 533 energy to purchase, which is a considerable amount.
So, the idea is that you make a new knight and bring it to and complete those missions as fast as possible. If you can do it faster than you can grind 533 E on your main, you're profiting.
Of course, this method would have some problems. For one, recipes would not be usable several times as you have to make a new knight each time you want orbs. Unless you find orbs on the new knights, you'd have to purchase one extra orb for every new knight to be able to do three crafts instead of two and leaving the knight with two spare orbs.
I'm gonna try and see how fast I can get a knight to these orbs some day, sooner or later.
Thoughts?
Already did it for my Arc Razor.
It took me about 4 hours to get the Advanced Orbs of Alchemy needed to Craft it.