Agility > Critical Strike = Haste = Mastery > Versatility
Agility: Increases the magnitude of your attacks and abilities. This is your most important stat, which is why you want to look at the item level of each item rather than the stats on it. A higher item level is usually better because it gives more agility.
Mastery: Your mastery is called Mastery: Master of Beasts, increasing the damage done by all the pets and creatures you summon. This includes your main pet, Dire Beast, and more. It gains much value in AoE situations because you have way more pet damage in your DPS breakdown (Beast Cleave, Kill Cleave, Stomp, etc.).
Critical Strike: Increasing your chance to critically hit with all spells and abilities. BM Hunters have another passive interaction with Crit called Wild Call. If your auto-attack crits, it has a 20% chance to reset the cooldown of Barbed Shot.
Versatility: Increasing all your damage and healing done also decreases all damage taken. This can provide a bit of survivability that is sometimes needed for hunters.
As for tertiary stats, Avoidance is the best one, since it reduces your damage taken from a lot of different abilities. Speed is a neat stat to have on your gear, especially if you decided to go for the Acidic Hailstone Treads.
Leech is more or less useless, since most of the damage is done by your pet, hence healing your pet instead of yourself.
The best way to calculate stat priorities for your character is to "sim" your character. Method Raider Jaerv has written a series of Metafy articles to help!How to Sim in World of Warcraft
- Tauren: Since your main stat priority is catered around critical striking, Tauren’s 2% critical strike damage pulls ahead in every scenario. War Stomp also provides a casted AoE stun, which can be useful in a lot of content.
- Orc can be a strong contender (especially in AoE) thanks to Command passive, which gives you pet damage and Blood Fury that can be lined up with Bestial Wrath and Bloodshed.
- Dwarf is the best race for Alliance for the same reasons as Tauren, the difference being the active ability Stoneform providing a 10% physical damage reduction with an added omni-self dispel on a 2 minute cooldown. Dwarf is definitely the best overall option, and I highly recommend it!
- Night Elf is another option, granting 1% Haste during night time, and 1% critical strike chance during the day. The active ability is Shadowmeld, which lets you drop threat from all targets instantly. You can use that ability a lot in Mythic + and even on certain raid mechanics, to completely interrupt or ignore them.
Chest: Enchant Chest - Waking Stats
Legs: Fierce Armor Kit
Ring: Enchant Ring - Devotion of Mastery, Critical Strike, Versatility or Haste (depending on your stats - SIM yourself!)
Weapon: High Intensity Thermal Scanner
Headpiece: Incandescent Essence
Every gem with 2 different stats works (these provide more stats than the single-stat ones). It is situational and will depend on what stats your character has at the moment. The best way is to SIM your character on Raidbots to see which stat you need the most. Make sure to have 1 Diamond equipped (this one is more powerful).
Rune: Draconic Augment Rune
Healing potion: Dreamwalker's Healing Potion
Weapon rune: Completely Safe Rockets