Another Call for Advice

I know everyone has been posting here like crazy asking for help deciding on which banner to roll for the GSSR (I really hope DW doesn't change things up for us compared to JP, lol). I was hoping that I would roll a Merlin and make my choice easier, but he decided not to come visit me. I've decided to save the last of my Quartz for the GSSR with a few extra left over for rolling on the next banner.

But I'm torn between which one to get. I think I've narrowed it down to either Caster or the Assain+Ruler banners. I don't have any 5* Assassins, and none of the Casters from the Banner

I've been playing since shortly before the first Halloween, so I have every Welfare servant, so I won't bother including them on my list:

Casters: Ilya, Marie (Summer), Nitocris (NP5), Nursery Rhyme (NP3), Medea (Lily) (NP3)
Assassin+: Carmilla, Stheno, +Jeanne d'Arc

I've felt like my Assassin list is pretty weak, but I think that is mostly because the Assassin list in general is pretty small. It wouldn't really be horrible to get my Jeanne up to NP2, so rolling for Assassin+ seems like a good option. But I also don't have any of the Casters, so rolling for them to have the better support-role servants seems like a good choice too. Anyone have any thoughts?

Here are my other lists that I've essentially eliminated.
Lancers: Tamamo (Summer), Vlad III (NP2), Elisabeth
Riders: Drake, Anne&Mary, Martha, Marie
Berserkers: Raikou (NP2), Beowulf (NP3), Frankenstein, Tamamo Cat, Lancelot, Heracles

I've had some pretty good luck in the Saber&Archer areas, so I won't bother posting those lists.