That being said, OP should know the other side of the medal- people who spin over 500 and dont get them. There was a mod on forum who posted spins (1500) and no jackpot. Recent Kaizer's video- 500 and no jackpot.

1. nobody knows the drop rate

2. server can get either 50 minatos or 0. There is no set ammount.

3. Make assumption, that you WONT GET minato or that there is no jackpot at all in this event. Would you still use your resources to spin that wheel for the items? If yes, keep spinning, if not- don't.

RNG events have one rule- use them only if you like common items that are inside (or redeemables in lucky stars case) so you have no regrets. Jackpot is an addition, not main goal itself. Since you are ftp and you seem to really care about getting minato, save more and buy his frags directly in evets like lucky board, mission dealer or treasure of the sages.

That being said, if you have a lot of ninjas and you dont really care if you get one more or not, because it creates JUST ANOTHER team, rng events tend to be one of the better events. I'm speaking from personal experience. Spending resources on power is good, and if you get ninja you dont have as an addition- even better. However most of the playerbase cant get it, that if you arent in a comfortable situation that you already have (one of) the best meta teams available, you should really avoid those kinds of events. First work for a solid base team, then you can experiment with RNG, because if you dont win, you arent left with nothing.