This all depends on who you use as your main slime, Slimes get x2 Main attack , Main HP and Main Skill damage from having their own Toy.
Not all toys are made equally
Each toy has 2 main stats 1 main skill boost and 3 three stats, the two main stats are always Attack and Health, and the skill stat applies to the slime unique skill but the 3 sub stats are randomized and are unlocked at different fusion stages
Stat slot 1 comes with every toy and is on common and above-grade toys
Stat slot 2 is unlocked at Epic level fusion
Stat slot 3 is unlocked at mythic-level fusion
Each toy grade has a different level cap and requires a different amount of clockwork to upgrade getting more expensive as you get to higher levels with each upgrade you get +20 levels to the next level cap up to a max of exotic level 140
What’s fusion and when should I fuse my toys
Fusion is the game mechanic to increase the grade of your toys every 3 toys of the same grade can be fused together to create one toy of the next grade, exotics being the exception they only need two exotics to be able to fuse to create another random exotic with random stats but this is not recommended and is an extremely inefficient use of your resources.
When you fuse a toy the toy you choose first will carry over its stats and level to the next grade and if you used any clockwork on the other two toys that you are fusing to it these will be refunded to you but not the clockwork used to level up the toy in slot 1
So what’s the best stats for a toy
Companion Damage – Companion Damage is currently considered the 1st Best Stat
Note: for F2P players running Skill Build 2nd best stat becomes 1st best and so on as comp damage isn’t used in NON :GradeSS~1: Slime SKILL BUILDS
Boss Damage – Boss Damage is currently considered the 2nd Best Stat
HP – HP is currently considered the 3rd Best Stat
Skill Damage – Skill Damage is currently considered the 4th Best Stat
As of the Talisman Update once you have level 50+ Legendary Talismans Skill damage in toys becomes optional and really only useful in glass cannon builds where HP is useless for a very small damage boost
Critical Damage – This is now a useless toy sub stat due to the crazy amount of critical damage we now get from magic items making the critical damage gained from a toy meaningless
Attack – Attack is currently considered the 1st Best Stat ONLY FOR
Slime Toys UNDER LEVEL 95 Do not take these past legendary once you can make a toy higher than level 95 it’s time to go for the stat priority above
TLDR; Best Toy in Most Cases
Matching slime toy
Companion Damage
Boss Damage
HP or Skill Damage