I'm a newbie who just started

The limited character Wishadel is super strong! For permanent characters, Silverash is super strong!!

Raising a 6-star unit is quite tough, so I recommend focusing on 3-star and 4-star units first! To progress smoothly through the story, make sure to level up Amiya (or your favorite character alongside Amiya if you have one)! As an early player of the global version, I personally think Mountain would have been really helpful early on. He has a Vanguard-like cost, and once you activate his S2 skill, which can be used immediately, you can take your time placing other units. By the time you need to heal, he's usually still effective.