I'm trying to get past level 61, I'm curious to know if I should choose different sylesti's for my party to battle with as I'm still unfamiliar with how to tell which of my pets are stronger and more better for battle than others.

I appreciate any advice :)

The higher the base stats a pet has, the better it'll do in battle. If you've reached the Lost Grove already (or if you're almost there) you may wish to focus on your team setup a bit more. The Lost Grove has a massive difficulty spike and it can be incredibly tough on players who have gotten used to the earlier battles and have managed to get by without a healer.

The most basic setup is 1 tank, 1 healer, and 1 damage dealer (dps). I recommend you use this one for now as it's versatile and is capable of getting you all the way through the Grove once your pets are ranked up.

Earth is the most common tank with probably shadow as second most common and water as third.
Light is the healer.
Your DPS can be either air or fire. Air pets focus their damage on a single enemy while fire pets do damage to multiple targets at once.

I will quickly note in addition to what Sakina said, max stat pets are in no way necessary , but starting off in Lost Grove with pets on the lower end of the stat spectrum (<50) can make it a lot harder (primarily because lower stat pets generally have quite low HP, and sometimes mana too)
Once you start getting better LG equips and ranking attacks on a pet, lower base stats is less of an issue, but if you're just starting out you may want to see about getting a team with base stats 50+ just for the initial push/getting used to lg


also as mentioned, typical team build in lg is tank/healer/attacker, though later on when you have more experience in lg people can branch out a bit more.
You'll pretty much always want to replace any non-LG gear you were using with the applicable LG equip type for whatever element asap since even the lowest tier of LG equip (the Exotic/rare tier) are better than most non-LG equips
(LG equip tiers: Rare = Exotic, Epic = Vinethorn (VT), Legendary = Stoneweave (SW), Mythical = Primal.
Exotics are fairly easy to get your hands on, and VT's are somewhat easy but can be somewhat pricey. SW and Primals are likely to go for literal millions because of their methods of obtainment, which are. Complicated.
You might also occasionally see things like +[number between 1 and 5] on an LG equip in the broker, which are equips that have been Upgraded, and thus have better stats than the un-upgraded versions, which also go for fairly hefty sums)


Tanks (pet goes in Slot 1 of the party, proficiencies will be in some combo of HP, offense, and Agility):
Earth (equip with lg equip type Warden, or Tidal Lord)
Shadow (equip with lg equip type Reaver, or Lightbringer)
Water (equip with lg equip type Tidal Lord, or Warden)
Light (equip with lg equip type Lightbringer, or Reaver) (don't recommend starting out with a light tank initially, since generally they're covering both the tanking and the healing and they'd likely find it hard until ranked)

Healer/Buffer (Proficiencies are typically 3 offense, 3dex, but they may also get some HP in place of dex):
Light (equip with lg equip type Pyromancer, possibly Lightbringer) (Light healers generally want dex (accuracy and crits) over agi (evasion and defence)
Water (equip with lg equip type Storm Caller or Tidal Lord) (probably better left until the pet is lv75 and has access to Wruen's Blessing's passive effect, not really easy to use if you're newer)

Attacker (Proficiencies are typically 3 offense, 3dex. an HP instead of dex is rare but not unseen):
Fire (equip with lg equip type Pyromancer)
Air (equip with lg equip type Storm Caller)


What team are you currently using, where are you progression-wise?

may i ask what tank is?

A tank is like..the defender of your team. The one that has the most health and survives the longest and the one that takes most of the damage (slot 1)

thanks!