like all other question, this one is about tips for GSSR

now, i brought the sq, so i am in now for this gatcha.
i reserch the banner, and i compared it to my chaldea to see in witch banner i should pull.
I came to this conclusion.
Caster Or Rider. Pretty common, i know.
Now here come the problem
I love all of rider in the banner. Even if a end up with Madb i will be fine, happy even becouse i would have her side my cu.
Frencis is my big sis since fate extra, ozy would be awsome bot for farm (np team battery, something i really lack) and for my cleo. Quez is kuku, so she is awsome.
And i have no good rider! so i would be fine with any really.
But.
Caster have waver.
If i get him, my team would become so much stronger.
So many more strategy with my own waver.
But i would end up be disappointed in both tamo and xuan...
they are both great, but i have strong st berserker and gil caster.

So, the point is. Waver would improve my chaldea a lot, but is 1/3,
any rider would be good, but is not even close to be as good as waver.
So, should i risk or not?
and by the way, when exatly is this banner?