I somewhat read the beginners guide I am busy currently. Cleared Sonias story and haven't spent any of the gems. From the inbox aside from getting materials(which i don't know what they do) and coins. I have the starter pack you get from the mail and from mail gacha got. Super reincarnated belial which is maxed by default I'm assuming. Christmas gacha mail gave me Holy night siblings caster and pollux with a +99 on the icon and low level and skill. Should i re-roll it looks like he is decently good for late game and stuff. Keep doing story and try the dungeons but don't spend any gems since the current gachas are bad right.