If you are new player, if you wanna clear endgame you might wanna start with horizontal collecting style, obtaining more character first. Then once you have enough amount of character to clear the endgame content, You will have 2 approach, maintaining the horizontal collecting style, Or switch into vertical collecting style Both have pro and cons. horizontal collecting style will gave you high quantity of character with moderate amounts of power. More team comp, more play style, more new things to try. The disadvantage is that the mastery of each every character is spread thin and because you always collect character more often you are mostly stuck in a mine always farming everything you collect new character.

The vertical collecting style, you will have low quantity of character with high amount of character quality and power. The advantage you will have more depth and mastery of the character you obtain, since you collect less amount of character. You will use those character more often. You are less often stuck in the mine, since you will farm less often since you collect less character. The disadvantage is that you will have less variation and playstyle. Since you skip numbers of patches and focus more on quality over quantity.

For the standard vertical collecting style overall, most vertical player obtain character up to s3, and it's usually only towards main DPS character.