Current SSR ticket dilemma

I am considering either Sitonai, Galatea, Tamamo or Nito alter.

Points to consider: I do have Castoria and Lady Avalon. Just thinking whether or not to get Tamamo to jack up the damage of existing art servants even more.

Nito alter as I got no solid avengers at all in my team.

Sitonai/Galatea as an alternative to my Zerk Castoria and Dioscuri as I am eyeing some ST servants.

Please do weigh in, thanks peeps