You need 495k medals for all the 330 high ampules. With the 800 medals core, you have to do it 619 times for 49500 stamina. For me, 1 pot gives 216 stamina. I need 230 stamina potion per month to run the core 619 times. That's a lot of stamina potions and times.

To farm this stage, I use my regular farming team with White Tulip (medic)/Spring Star (school)/Asian birch/Adlay/Tritoma. They take care of everything. I just need luck to get some react on White Tulip/Spring Star/Birch/Adlay to bypass all the negate damages on phase 1 or Tritoma isn't able to kill it in one turn (meaning she will lose her buffs for the 3rd phase and taking way too much time).
I shoud try with another girl with 100% react instead of Tulip or Birch.