Wow im a bit dumb
I need to level up quickly because I just bought a too high level pet for a place I'm stuck at(garden of the magnates in the second area)
Help

What pets do you use in your party? (since you don't currently have any actually on it)

You having bought a pet of a high level makes no difference to anything, you just cannot put a pet with a level higher than your user level* in your party
(*which is in turn determined by the highest level you have raised a pet to on your account)

My 3 main rn:
doing missions
https://www.sylestia.com/view/pets/?petid=7137540
https://www.sylestia.com/view/pets/?petid=7137547
https://www.sylestia.com/view/pets/?petid=7139213

1. Make sure shadow pet is in slot 1 to tank properly

2. gear
Shadow pet has two disciple equips and two Myrmidon. Disciple is fine as placeholder, but Myrmidon is Air Attacker gear, and the opposite of what a shadow tank wants, since it boosts Strength and Dexterity, when the shadow wants Intelligence and Agility

Light pet gear is generally the right sort of type in that Illusionist and Evoker both boost Intelligence... but the relic is Myrmidon, which, again, Str/Dex equip, and especially since it's a Relic, it's giving its Damage boost to the wrong attack stat (Light pets are a Magic element and don't use the Physical Damage stat at all)
You'll want to replace that with an Illusionist or Evoker relic (or Disciple failing that) asap.
(to show the point, her damage stats look like this currently:
Physical Damage: 209
Magical Damage: 71
with 145 of the physical damage coming from the relic damage boost.
She as a light pet can only use Magical Damage stat, so all her attacks are running off 71 base damage rather than 209)

Fire pet is fine (although a fire element won't as easily let you use the dominant strategy for wave battles, which is to focus on a single enemy slot to force the stronger enemies to bottleneck and only come one at a time)

Might want to look to replacing all the rare equips with lv25 legendary gear, since that's easy to get, although they're nearly lv50, so might be more point to just waiting and then going full lv50 epic/legendary

3. profs
No point to all of them having hp profs- those are almost always only on tanks, save specific player preference. Light, you'd probably want 2int profs, fire, either 2int or 1int/1dex, so they have higher move output (meaning better healing from light, and better damage output from fire)

alright, Thanks!