Depends on how much protection do you have. And how much you will to sacrifice for this skill. If you don't have too much and/or you wan't to Trial other strong ninjas, go for fragments.

Agreed

i'll say if you don't have enough vials just buy some vials because its more cheaper and you can get a lot of vials on great plates

Depends if you can afford the frags needed for the last sb .

You are somewhere along the 20k coupons for the garanteed last sb.

Now take into account that you will need 4 prot per try and that you are on the worst possible situation currently : There is only 1 better outcome for a 1 vial 4 prot cost .

You may get the last sb quickly or it may requires 30+ vials (and 120+ prot ).

Previously I had 400 protection vials =100 chances

But it didn't change a single bit but instead I lost that +1

After few days I tried again with 20 or 24 protection vials I got +1 again.

So I am wondering that do I need 800 protection vials or more.

I'd remove one of the protections so you have a better chance if you do 2 trials. Then decide how many you prots you will feed the rng with. If you don't manage get to collecting frags. Anyway ninjas get out of fashion faster these days. Previously we had cycle of about 6 months now is about 2-3 before a new ninja comes out to take the top spot. I remember that I played Edo Minato for about 6 months as he was quite relevant. Then Madara 10t retired him partially. Then Madara GNW came in, Then Kisame. Then think how quickly there was Obito trials, Naruto 6p and Madara GNW. Now we have Shisui who broke the game again. XD. I am just curious what will kill Shisui.

The point is - I don't get my head *ing too much to one ninja. I now go for variety.

Agreed