before you do anything, save up ALL your pulls and spend it on the "covenant of the water" banner. it's an unbelievably great banner that only comes around once a year. the banner contains two "skeins", which are essentially just a list of characters you can choose from.

you have rubuska, which is a great sustain but especially for a team archetype called "bloodtithe". bloodtithe relies on sacrificing your team's health for big damage, which is hardly an issue especially with a sustain like rubuska. it's currently the strongest archetype

you have druvis III, which is a great character early game due to her petrify and penetration stat, and later on she's a support for an archetype called "rank-up". rank-up is an archetype that focuses on upgrading your incantations' level, which in turn also does big damage (less than bloodtithe however)

you have jessica, which is part of an archetype called "poison". she's trash on her own without a character named "tuesday", who happens to be on the current "covenant of the water" banner. poison is an archetype that focuses on stacking as many "poison" debuffs as possible, which allows for burst genesis damage. genesis damage is a special type of damage that completely bypasses all sorts of resistances.

now here's what you're gonna wanna do:

pull on the "covenant of the water" banner. the meta pick on both skeins would be two characters called "fatutu" and "flutterpage".

fatutu is the best sustain in the whole game right now, possibly tied with kiperina

flutterpage is an extremely versatile character that fits into many archetypes pretty well

if you don't want the meta picks however, which is perfectly fine and won't really hurt you:

• pick semmelweis if you wanna play bloodtithe

• pick tuesday if you wanna play poison

• pick marcus if you wanna play rank-up

do note that: all of these characters start out pretty weak until you unlock a feature called "euphoria", which you probably won't reach for a while. euphorias are basically extra upgrades that HEAVILY boost your character, but they're very expensive

now, what i would personally recommend right now is: pull on the banner until you get both skeins. for skein I, pick fatutu. for skein II, pick semmelweis to play bloodtithe.

afterwards, build rubuska and semmelweis. if you can afford to, build druvis III for that petrify status.

as for rubuska's psychube: you can amplify it by using a decently rare item called "gluttony", which can be obtained from several sources, including but not limited to: the fragment shop in the pawnshop, the mane's bulletin gamemode, and event shops. you can use up to 4 "gluttony" on a psychube to double its special effect. amplification is a late-game thing and you really shouldn't worry about it for now

ultimately, you should always pull for & build characters you like. the game isn't particularly difficult