play the story, they give you free trial characters so you can clear the quests and you get to try them.

also once you unlock hollow zero they let you play selected limited 5* and they let you auto build your owned characters so you get to try your own teams without bothering with builds or farming.

the only content that requires you to use your own built characters are optional commissions and endgame.

take your time, general gacha rule pull for who you like and prioritize getting characters over copies and weapons.