Notice: This tier list also includes units on JP server and takes their EX 120 abilities into consideration. Units are not sorted from best to worst.
Missing units, wrong ratings, or any input can be given in the comments.
SS: Gamechangers / Meta Defining. S: Top tier. A+: Good outside of mono teams and has useful buff/debuffs to help the party. A: Fairly standard, but still good in mono teams. B: Situational. C: Outdated.
If you want to reroll the game, check the reroll page instead, since this list includes many limited time units that are not available in the gacha pool.
tier list is outdated for those wondering, it's also mixed with JP and GL units which is very weird, tiering up characters that exist in one and not the other on the same tier list together will result in inaccurate rankings. There are also differences for characters between servers as well (ex. Starlight Elena).
It depends on what you're planning to do with your account. Yuna is a good healer (she is one of the best back then), if you don't have a healer you may go for her. Auron is ice slash attacker who may help your ice team, he is good but he is not OP units in my opinion. Well, if you like him you can go for him. You can pull units that you like.
It's because this tier is updated sometime. Tidus was released one year ago, he was the first collab character to have an EX (lv 120) and he was one of the most used unit back then, he can also be a tank for water team (where Celes hasn't exist yet). Of course, compared to new 100 cost unit and recent collabs, he looks like "outdated" but he's still a good free unit.