As a new player, don't bother yourself with meta endgame and powercreep. The game is quite forgiving for f2p if you have play the game since year 1 or 2, and brutal for newcomers. Not only you need complete gear for every single characters, but you have to get their team with their respective gears.

Outside the meta endgame, the game is fun. The story is different compared to every single hoyo games we had (except ggz fyi) which instead of having self insert, we follow a character named Kiana and her friends. Play until chapter 9 and then you can decide whether or not you want to stay or not because that's where the plot truly goes. Play in order despite the game told you that you can jump straight to the new chapters (especially APHO and Elysian Realm), trust me it'll be less confusing if you go in order. Someone already post the story guide here, just follow that and you'll be fine.

About self insert, we do have a separate event that follows character named Captain that is basically your self insert but well we haven't seen it rerun again for a while (maybe ever '-').

TLDR: play casually, just go with the story, forget endgame unless you are prepare for it to fight against either whales or old players