The best recharge event is when there's double recharge, like last week (recharge wheel + daily recharge). You could recharge slowly every day to build ingot for jonin.

Spending event varies. For example, the daily spending event two weeks ago was kind of good. Jonin medal isnt big enough to get the really good rewards from the total spending rebate.

There is from time to time a jonin medal rebate. That's the best time to buy it, as you will get something like 33% of the ingots back as coupons.

Jup last week was the best recharge. A good spending event is balloons imo.

I don't know if there is a specific event that favors a time to buy the jonin medal. Maybe the bimonthly Jonin Renewal like someone suggested.

I would def wait for a solid recharge event where you get lots of coupons for -only- recharging. Watch out for the scam that requires you to recharge + spend ingots to participate.

As far as spending ingots goes, there is never enough patience. I believe the best return on spending is to renew the monthly coupons if you truly do not wish to invest further.

The best Recharge rebate would be when you have jonin medal rebate together with shurikens and spending rebate i think.