Many of us may have noticed that SP made some changes on special coins collection (72-hour-challenge and maze). After several days observation, I found the rules have changed, and I just want to share my experience here.
My level is 54. I used to be able to collect a lot of coins from repeating growing the cheapest food, now I just need to do this one or two times per hour, getting 12-20 coins per hour. (But there is a problem, sometimes there is no coin from normal collection, unless I grow blue lizard's tail once more on one farm and collect it) Same rules for the gold collection and feeding, totally about 10-20 coins per hour. (If there isn't any, keep collecting or feeding until the coins pop up) I can get coins from PVP only once per hour, 3-10 coins per win. No coins from breeding or hatching. So normally, I need to check my game once per hour, and I can collect about 50 coins per hour, and about 500 per day.
With this speed, during the Eldritch's Abomination Maze activity, I think I can get Sludger, Postiguraf, Invidia, Ophiuchus, and Yilitre, without buying any maze coins.
If you are not getting any coins from normal collection on your phone, try facebook version. It works for me.