I'm very new and I pretty much just started the story. You have a choice during the story at Fungus Grove to either negotiate or fight Cereth. I chose to fight him. Now I can't get past him because I die right away. Is there any way to undo this or do I need to just grind until I can beat him? Thanks.

The fight with Cereth is unavoidable- the only difference between the two options is the text that you get.

First question: Do you have your second pet slot unlocked? If you don't, you can buy it from the Esior's haven plaza
(if you don't have the gold to buy it, you can send pets on missions (see guide to mission pets and missions), grind one of the earlier areas in region 1 such as trollsblight cavern to collect gold from boxes and sell equip drops, do stuff from the fest task list (nurturing 100 pets will get you 50 sun tokens, which is an amount that at present would at present time fetch over 12k gold), go through the fest zone collecting chests for their contents (and given your pet level also, you'd only be encountering mostly 1-enemy mobs with the occasional 2-enemy mobs, and no 3-enemy mobs if my experiences would hold true- 3-mobs only seemed to start appearing at ~lv25- and all mobs are scaled to your highest level in party in fest zone)


Second, do you have any asassin or other gear that boosts Strength? Water pets like Mist are typically tanks, and want Strength/Agility gear like assassin equips.
Especially the relic- I grabbed a lv15 assassin relic off of the broker fr you that you should give her, as currently she has a Magic-type relic. She's not able to make use of the boost the relic gives to an attack stat since she's a Physical element, and doesn't use the Magic Damage stat at all.

Water tank > slot 1 > gear that boosts Strength and Agility where possible
Air attacker > gear that boosts Strength and Dexterity

You might find use in a Light Healer or Tank (int/dex or int/agi equipment), since they're the only element that has any party healing abilities up until water hits lv30

Thank you so much for the information and the relic! This just shows I still have a lot to learn haha. I'll be sure to check out the resources you provided and my options. Thank you again! :)

I suggest also checking out this guide by Unstaeble- namely, post 2 and 3, which go over the most typical element setups (the other sections won't be something you need for a good bit, since the guide itself is set up for helping people with a much later bossfight)