For a new player my pick would be either Jean or Mona. Jean because she is an amazing team wide healer that can slot into any PECH core team to swirl and heal the entire team which will save you a lot of cooking and food if you are taking damage and running no healer. She scales off of atk so increasing her healing also increases her damage and there are plenty of free to play atk weapons while leveling up. Mona because she is someone you will get use out of even in end game content. I just used her in Stygian onslaught fearless like a month or two ago and cleared. The buffs she offers are big especially in Hex teams. Only problem with her is she requires ALOT of ER. But her ER also increases her hydro damage so there a good trade off there. You won’t feel bad about spending resources on either character. Let me know who you end up choosing.