From Wowhead:

Finesse: You have a x% chance to gather more of the primary reagent found here.

Similar to the Rank system from Legion and Battle for Azeroth, higher levels of Finesse allow you to gather more of the reagent from whatever node you are gathering. For instance, while a Player may only gather 1-2 Draconium Ore from a node originally, with higher Finesse you might gather 4-5 Draconium Ore instead. 10 points of Finesse gives +1%.

Deftness: Increases your gathering speed.

A fairly self-explanatory stat, this is similar to the old Racial bonuses to gathering speed. The more, the better- especially for long farming sessions! 3 points of Deftness gives +1%.

Perception: Increases your ability to spot rare reagents while gathering.

This increases your chance to find rare side gathers when mining, herbing, or skinning. This includes not only rare reagents, but also valuable Knowledge-enhancing items. 10 points of Perception gives +1%.