How should i prepare from Camelot

current servants

TLDR: new to gacha games nd i need help understanding the mechanics...

this is my first gacha game so I've only rolled for whomever i found cool(got Artoria from the free SSR thing) all servants are np1 except Gil is np2 (got 2 Gils on my first pull lmao)

I am currently in Okeanos and so far the story combat is extremely easy, though i heard it gets really tough in Camelot, so far I've been mindlessly rolling, upgrading and playing byt I'd like to prepare for the harder parts of the game.

Any guides or videos i should go through since i don't even know how combat works except the green blue red cards thing.

And can the game be beaten without having to grind? I'm in for the story not the gameplay.

Thank you everyone and sorry to bother you!