Core problem: Collars change stats and ability pools at the start of a run, but kittens only inherit base stats, the 3 to 7 numbers before any collar, mutation, or level-up. A 4 Strength kitten given a Fighter collar stays mediocre. A 7 Strength kitten becomes a problem. Farm high base stats first, then slap the matching collar on the kitten that already has the right numbers.

1The Three Classes and What They Want

Fighter
Wants 7+ Strength, decent Speed
Just hit things. Reliable carry once it has the Strength base and later passives like Merciless. The safest default class.
Tank
Wants 7+ Constitution
Strongest early for push and survival. Plateaus unless you specifically breed contact, thorns, or self-sustain. Many players drop the dedicated Tank once they have 6 to 7 CON cats of any class.
Mage
Wants 7+ Intelligence or Charisma
Useful for groups and elemental tiles. Benefits from fire and lightning more than ice according to players who ran it late.
Four starting collars: Fighter, Tank, Mage, and Hunter. You can swap them every run. The approach is the same for all: farm the base stat first, then match the collar.

2Get Usable Fighter, Tank, and Mage Kittens

3Key Decisions

ChoiceWhat players do
Which collar on this kitten?Match the highest relevant base stat. Enhance what they are already good at. A high-CON cat wasted on Mage just eats the Mage's CON penalty.
Keep or cull?Plus 1 per desirable high stat or useful mutation, minus 1 per bad trait, minus 3 for crippling defects like confusion or immobile. Anything below your cutoff goes to Tink or the pit. Raise the cutoff as the colony improves.
Inbreeding vs new blood?One generation of close breeding can lock a 7, then immediately out-cross with an unrelated stray. Continued inbreeding stacks defects.
Team composition early?Many default to Fighter plus Tank because they feel safe. Later they drop the dedicated Tank once they have 6 to 7 CON cats of any class. Mage stays useful for groups and elemental tiles.

Common Mistakes to Avoid