Erm...
Help?
Fire Eyes is CRUSHING me and I be like
*why doesn't this morkk dieee*
Does anyone have some helps fors mees?

I've only really used the Arena once, for a task, and that was a long while ago, so I'm no expert on it but we can say at least a little. (there's probably a guide somewhere to Arena strategies)

Since you have ShadowFlower, Crystalline, and Atlantis on a party right now and they're lv24, I'll assume they're the team you're using, since you didn't link/name what pets you actually are using.

> Earth and Water are both primarily Tank elements (I have no idea which is the tank in this case, since one has HP and the other has Agi, which are both primarily Tank stats)

> raise the team you want to use for it to lv25 and then use philters of unlearning on them to prevent further exp gain

> desperately need better gear. At the moment they have a mishmash of equips, both type and rarity (uncommon/green gear = Bad).
Tank pet should have Agi (Assassin, since this is an all-phys team, so you want str/agi)
other two should have Myrmidon to get the buffs to str and dex (unless the earth ISN'T the tank, in which case it might also want Assassin for when it Taunts and needs higher evasion?)

Getting them to lv25 means they can equip lv25 legendary gear (from lv25 Very Hard mission reward satchels and dungeon bosses mostly, and the trade broker) and lv25 mythical gear (if you get lucky at a dungeon boss, or lucky in the trade broker)

...ok,
I'll try to do that!
My normal team is Aravis, Brightflame, Estrella, but they're too high level, so your assumptions are correct. :)

*rubs hands* Oh boy. It's time.
This is a solid, though slightly outdated arena guide.
The Arena is a long round of gear and tactics, but I just need to start by stressing the importance of gear and decent base stats. You cannot just use any wild non LG pet for the Arena.
But first, tactics.
Like in the LG, watching the buffs and reading the battle log is important. When Fire Eyes gains Heat of the Moment (little red icon under his mana bar) block with the main pet, otherwise it will crit and hard. Generally does about 500-600 damage, I believe. (that's why health lower or equal to that is unsafe...1-shot kill even when blocking.) The icon stays for the turn after, ignore it and just keep hitting with the main attacks. When health gets below 75%, heal with Mend but don't Mend before that. After the second time the Heat of the Moment appears (as in it appeared, you block, it stayed for another turn, left, and now appeared again and you block) use Finishing Blow on the pets with decent health or Mend on cooldown.
I'll be back in...two hours, when I can check how much health Fire Eyes actually has.
Onto stats!
That guide said all base stats 40+ and preferably decent health. For your tank, you're going to want more than that. Meet my party because I don't have permission to reference anyone else.

700 base health, 120 mana, 56/58/50/50 in other stats. Proficiency goes in health. For all level 25 pets, unless you're using maxes (2000 base health). I strongly vote shadow for the tank. While the guide says you can get through Fire Eyes with only Rare level 25 gear, I used epics and legendaries. Can't be overprepared, haha. Illusionist is best for the tank, since proficiency is in health, we need all the gear-stat boosts possible.

Second position is a healer and sort of side tank, which is a personal choice. I don't regret it, it's pulled the team out of several scrapes (Kimeria and Katalyst, 3rd fight, mostly, I think is the hardest 25 fight under Oogar, 5th fight) with the 50% heal. 640 base health, 100 base mana, 38/40/44/48 in other stats. Again, proficiency in health. I would not go into the Arena without a pool of 10k+ health. I have this one split between Evoker (dexterity for crit bonuses) and Illusionist (sometimes it comes down to the healer and the damage dealer after the tank dies, and we need some evasion).

I actually chose Wind for damage, because usually there's only one opponent, and the Bleed is fantastic damage. It stacks. 620 base health, 100 base mana, 43/44/42/44 other stats. Gear is split between Assassin and Myrmidon because...that was all the legendary physical-based gear I had on me.

What does this mean for your pets?
Atlantis is...not up to par. If she was 4/4 boosted, maybe. Certainly not as a tank. Crystalline...I could complain about the health for a bit, but nothing epic gear couldn't fix. Could also complain about ShadowFlower's health, but other than that, those two are fine stat/mana wise.
Check your gear. Assassin+Myrmidon is for physical damage. Evoker and Illusionist are for magical damage. Arcanist and Ravager are very risky and I do not recommend them, while it gives a large amount of power, it detracts from evasion+crit chance. Which gets very important later on (Oogar, mainly.)
I have never actually played with an Earth tank in the Arena, as their inability to continually self-heal (Siphoned debuff on enemies, replenishes health for 100% damage dealt) forced me to be less reckless than usual with party health. But I can recommend that you either swap out Atlantis for a light pet, second position, or a higher-statted tank, 1st position.
And everyone needs proficiency in health. Everyone.

Sorry for the word vomit, the arena is a thing that I...have unhealthily aggressive opinions regarding.

how do I level up faster?