Is there a best in slot GS and armor that goes with it or is it situational?

The most popular combo is Controlled Current Technique and Ashes of the Embersoul with % usage BiS Best in Slot data provided by Wowhead's Beast Mastery

A Hunter's Guide to Pre Raid Best in Slot : Classic WoW Tutorial

best in slot blood dk best items available at that level are for Hunters For each slot, I'll list the absolute BiS

best slot machines at plainridge Hunter BiS List ; Finger , Frostbrood Sapphire Ring, Valithria Dreamwalker 25HC ; Finger, Ashen Band of Endless Vengeance, ICC Reputation ; Trinket