What we have today
While there's no calculator yet, the Slime RNG luck guide documents every verified luck source, every single-source value (Luck Boost = 2x for ~3 min, etc.), and every multiplier that's still unverified. It's enough to plan a stacking strategy manually.
For free permanent luck right now, redeem the active Slime RNG codes and rebirth as soon as it's comfortable. Those are the levers we have actual numbers for.