Assassin + Extra Class:
I already have Jeanne and dislike Jack.
Chances: 100% cringe
Berserker Class:
Since my account features Vlad, there will only be a 66% chance to get a new 5* Servant. Nightingale is an eye candy, but won't see much use in my opinion. I'm neutral towards Cu.
Chances: 33% despair (Vlad), 33% eye candy (Nightingale), 33% it's something (Cu)
Caster Class:
I have none of the 5* Servants and would kill for a Waver <3. However, I'm not a fan of Sanzang and neutral towards Tamamo.
Chances: 33% jackpot (Waver), 33% meh (Sanzang), 33% it's something (Tamamo)
Rider Class:
All of the 5* Servants are missing in my team. But Coatl didn't pique my interest in Babylonia, I'm not a big fan of Drake and have absolutely no opinion towards MedB. Ozy on the other hand would be phenomenal.

Chances: 25% jackpot (Ozy), 75% I don't care (MedB, Drake, Coatl)
Archer Class:
I have Gilgamesh. Enough said. Not to mention that Arjuna and Orion also found their way in my team (without my consent though...). I won't elaborate on Tesla.
Chances: 100% despair
Saber Class:
Altera, Altria and Moerdred rejected me ever since. Obviously, I wouldn't say no to them, even though they are not the most powerful Servants in this game (anymore). Besides, I'm missing a decent AoE Saber. But with Okita and Rama at my side, I'm not in dire need for a new Saber.
Chances: 100% happiness
Lancer Class:
Another Class where I am missing every possible 5* Servant. Karna was one of my favorite characters in Apocrypha. Altria is Altria.

I'm also amazed by all three skills of her. Her character skin (on the horse) is quite cool. And as a Gilgamesh owner, it's only reasonable to look out for Enkidu. : )
Chances 100% happiness
I can't go wrong with the Saber and Lancer Class, even though it pains me to let go of a 33% Waver or 25% Ozy chance. It will be Lancer Class for me, because they just seem more "flashy" in my eyes.