Try your luck is not really good.

Best is obv. Monthly Cards and Froggy. If you are stong buying extra attempts on Plunder and Convoy is good too.

Also: don't sleep ok buying additional Myoboku Trial (the game) attempts.

Those are - with the exception of froggy - low spending events. If you wanna use your ingots wisely, do it in events, which give you a nice reward for using ingots.