Great plates event.

Thank you, how much should i collect? And when should i stop using them?

Those are situational for everyone. You can never have enough and you never stop using them until you are satisfied with your team.
You can "stop" once you have completed every breakthrough on every ninja you have.

Thank you-

Hmm.

I do agree with them. The best way to get Advance Vials and Protections is from the Great Plates Event. For the amount, we cannot say or give an exact amount that you should collect and when to stop collecting since using it to roll breakthrough skills is unpredictable. You may experience rolling some skills and get it all maxed within a few hundred but there will be absolutely time that you will experience using hundreds of it but it will not enough.

Now for using Advance Experimental Vials and Protections, I would say use it until you get 3 to 4 maxed breakthrough skills and after that, you may stop and rest for a while. It is common knowledge now that using vials with 3 or 4 locked skills grants you less chance to succeed in maxing the 4th or last skill. Some people chose to do it the fragments way than taking chances with vials while some people get lucky and hit the max ones but again, it is unpred!ctable.

Just to share, last week when Kisame [Samehada Fusion Mode]'s breakthrough was released, I used 300+ vials before I got a gold skill and it is not even the one that I want which is the passives. Right after getting the Gold Passive 2, it took me 300+ Advance Protections before I got the Gold Passive 2. All in all, I used 800+ Vials and 800+ Protects just to end up with 4 Gold Skills. I'm not saying that it is hard to breakthrough key ninjas since it will depend on each player's luck.

Thank you.

Thank you, and oh god that luck! is are the chances of getting the gold skills known, or are they random for everybody?

It's random. There is no guaranteed how much you need to get gold skills.