at Level 65 I'm getting around 17% per spin. I'm now pushing max bet of 25k/spin and flying through the levels. Sure enough, I hit an 8.9m jackpot and have been riding that for the last 30 minutes. I slowly made my way up to about 500k and bumped my bet up to 2500 and gave myself 50 spins to see if I got lucky. 500-1k bets seem to be the best options but as I pushed into level 30+ it was getting to be 3-5 spins per 1% level, which was going to slow things down moving forward. Update: I took the advice below and focused entirely on Bank of Jackpots.
I'll check back in a week and see where I'm at. I'm level 20 after 2 days of playing as much as my coins will allow me to play. I'm currently sticking to the quests because I haven't found a slot that seems to have a decent payout. The big wins are pretty uncommon but some of the slot gimmicks are fun.
I'm keeping my bets at 500 because anything more drains me fast and it takes a day to get enough to play for more than 20 spins. The biggest mistake I made early was thinking this was similar to the other slots games but the daily rewards are really low. I think I started this during the double rewards AdGate was running at the end of the week. I'm having a hard time seeing how this one is possible without dumping most of the $40 into it.