Next gssr

Should be on the 2nd anniversary.
https://fategrandorder.fandom.com/wiki/Fate/Grand_Order_Fes._2017_%EF%BD%9E2nd_Anniversary%EF%BD%9E_Lucky_Bag_Summoning_Campaign

But there's literally EVERY SSR that came out till then in the summoning pool. Even limited ones.
So it'll be just a roll to at least get a 5*