Originally Posted by
weras
We should also mention the Sacred crystals, and that you should keep a handful around for stamina and charisma restores for events, and if you want to throw them away, the premium roll is the only one that's worth it. The unit odds according to jp wiki are approximately
50% silver
37% Gold
10% Plat
3% Black
while the rare one is
70% Silver
26.5% Gold
3.5% Plat
1% Black
Keep in mind that you may be unlucky and never get anything other than Eunice and Mortimer though. You can also get extra silvers from the 2k gacha (~3.5% so like 1 in 32 rolls) but you really shouldn't rely on it if you are in need of a specific one.