Just started the game last night.
Lv. 20 best units I have currently are.
Dark Snake Kafka
Holy Knight Will
Clavier Kagamine Len
Dark Curse Lunaris
Twins LL & Mina
few other 3 stars and healers until I have enough points to put DCL in my group. Enjoying the game so far.
ID: 7205277419
Keep Kafka, Will and Lunaris. Will is still good and lunaris has a 7* evo next patch. Kafka is niche but at your level she is still really good due to her light/dark buffs.
Right now I think the optimum team is something like
Tridon lead
Zenia friend
Zedus
Libera
Aurelia
Krantz/Edea pending on what you want/need.
you can sub out libera with Nidora (whatever her name is this coming batch)
you can sub zedus for Michele since tridon would give her the 20% crit to make her buff cap
you can sub Aurelia for Melchio
Rhoa got instantly replaced by zenia but if you don't have zenia then he is still good
Glyph is a great lead too.
So far the great units you need for raids/trials are imo
Leads Survival: Tridon, Glyph, Bestie, Delmos
Leads Damage: Zenia, Glyph, Zedus, Rhoa, Raaga, Reis,
Leads Frontier Hunter (non mid/end farming): Ruby, Zenia, Raaga, Rhoa, Feeva
Mitigator: Edea, Krantz, (soon shera 7*) and Aaron (by far the worse due to his weak defense buff out of all the 7*), Elimo
Crit Buffers: Hadron, Glyph, Michele, Reis, Zedus, Colt, Kira
BB buffers: Zenia..forgot if Zedus does this or not, Nemethgear,
Attack buffer: Zedus, Michele, Shera, Hadron ( IIRC)
Defense Buffer: Kanon, Tridon, Elimo, Aaron (weaker), Aurelia (converter), Balgran (converter), Delmos
Receive BC when attack; Bestie, Libera, Medina, Kikuri, Diana
Receive BC on spark: Zenia, Rhoa, Raaga,
Cleanser: Edea, Aurelia, Krantz, Sagaravel (whatever his name is), Melchios, Kanon, Andaria,
Elemental Buffers: Glyph (fire/water), Krantz/Kafka/ (light/dark), Michele (fire/dark), Quaid (fire/water/lightning/earth), Libera (earth, lightning)
Increase BC drop rate (less useful in trials due to nerf to bc drop rate): Feeva, Sagaevela, Andaria, Griel
Attack down debuffers: Ruby, Griel, Kira, Zedus,
There are more roles but these are the important ones off the top of my head. Theres also BC cashback units like Bestie, and BC fill on turn (which is not nearly as useful on a lot of encounters due to bc wipe).
There are also some other good units like Balgran (debuffs + def boost that doesn't clash with pure def boost)
Basically a summary of important units. I know theres a few I'm missing.
Important roles that are basically required imo:
BC when attacked
Mitigation
Cleansing
Def buffer
BC fill on spark
and then some boost in dps like BB attack booster, Attack booster, Crit, elemental buffs.