kage edo jin1 jin2 lol treasures have the same rate of dropping itachi frags, so pull wherever you want. Edo treasure used to give 1-2 frags every 30 pulls but thats not the case anymore

Although it isn't the fastest way but might be a cheap way, itachi susanoo frags can be pulled from free pulls. So make sure you don't miss free pulls as each of them do count.

I will tell you straight up because I have proof of what I am going to tell you, and can back it. I finished my Susanoo Itachi at 60k BP, through the event Christmas in a Capsule, I.E. Dacing Capsule. This event is hands down the CHEAPEST way to obtain reliable Susanoo Itachi frags, other than Shinobi Feast. Granted I spent $2200 to finish him there ( I needed 57 frags) this is ultimately the cheapest way outside of the "free" frags you get from Shinobi Feast spins. The 2 frags you can buy in that event are priced at 800 ingots ea. In Dacing Capsule, 1 frag is around 400-650 ingots ea. I say 400 because that is around a 35% chance of getting the frag. But all around, I saved thousands of dollars going through this event over pulling for him with seals. Seals route is around 8-10k real money which is crazy. I suggest if you have it, to go through Dacing Capsules. That event is hands down the cheapest out of many of the others. DO NOT GO FOR HIM IN KONOHA GREAT TREE. It is way too expensive there. Also, the Dacing capsule event uses coupons as well. I spent 87k ingots for 57 frags. Seeing as you can spend coupons there as well, this would technically still be cheaper than pulling with seals. The only real F2P way of obtaining his frags are through the Dacing Capsule event, and Seals/Free Pulls. By the the time you finish him with free pulls, you could have saved the coupons needed in about 2 years for Dacing Capsule. Seeing as its around 40-50k coupons/year that you can get if you max getting them everyday. Free pull route will take you around 5 years to finish him.