If i remember correctly my method of choice was doing some live that gives a lot of money, and then use that money to do the dice rolling minigame. There is some way to get a 10% fan bonus on that as well, so a promotion should yield you 110k fans. Unfortunately it's a horrible grind fest.
Here is what i wrote in another thread on the topic:
Personally i farmed the RE:whatever quintet live, it gives a lot of fans and also a lot of money. The costume you get from the solo live after getting Iori to S rank is perfect for farming that live btw, since the image and type match, and it has a 30% money bonus, so the live yields over 19k.