I do not know if anyone has made a thread stating how to farm candy yet but I'm going to make one just incase people need help. I've gotten all three masks and so have my friends that farmed with me. I will now explain what we did to get the candy in about a day.
In the Iron Serpent Gate there is a Power Complex on the first floor. So, my friends and myself just went to this floor, solo, and when we encountered a "graveyard" as we called it we would just wait until the others finished and just invite each other and then we would trigger the Punkin King. We would usually get around 2-3 graveyards per run, in which case two people got 3 graveyards, three people got two graveyards, and everyone got at least 1 graveyard. After we finished we just went back up, we did not continue the gate, and we went back down to level one and did it all over again.
If anyone has any questions you can either ask up here or add me as a friend in game, my name is the same as on this thread, bloodmistmirage.
Have fun and good luck!
Right now there are 3 gates with a clockwork level on the first depth any of those can work if it cycles to them.