>>14749720I make 350k in one E4 run. Battle Money O-power level 3 and Amulet Coin. Use the O-Power for the first E4, you will have time to run to the next E4 to have it take effect. For the third E4, don't use the O-power. You should have regained 2 charges right now to get 6 charges again. Use it on the fourth, and then you'll be able to have the effect work on the champion. Much less work.
While you wait 30 minutes for the charges to charge back up to full after you do this once, you can just friend safari or something. The E4 run takes less than 10 minutes.