Rerolling doesn’t make much sense in a game like Lost Sword since the gacha is pretty generous and there are a couple selectors you can get in the F2P shop early on.
So I’m only going to recommend the best of the best units for people who want to have an easier start with their accounts.
If you are not willing to reroll for any of these units, it’s not worth doing it (unless you want specific waifus).
Tiamat is the strongest damage dealer in the game by far. She spams her Active Skill and has one of the highest base crit rates in the game.
Lancelot can probably catch up to damage output BUT she’s the first good DPS we get that scales with HP. Even if you don’t build a team around her, she’s still a beast.
NEO Bedivere is the half anniversary character. As you can expect from a unit on an important event, her kit is cracked.
The “lowest” priority on the reroll list. Merlin is an incredible hybrid support / DPS character that freezes the enemy and increases crit chance for all allies, a really uncommon buff in the game when it comes to character skills.
Don’t reroll for support units. Like I’ve said, there are a few selectors and plenty of random SSR unit tickets you’ll get when you start the game.
You can always pick one of them with those selectors instead.
Dian is the support for Knight (melee) characters. She shields, heals and buff their damage by a huge margin compared to other characters.
Galahad is a hybrid tank / support that applies a shield, immunity for 5 seconds and is the highest buffer for Ranger / Wizard units in the game.
In my opinion, is not worth rerolling for anything that’s not broken (Tiamat, Lancelot or NEO Bedivere), but you could settle with Merlin or one of the great supports mentioned before.