Critical Strike is generally your best Stat, but your Secondary Stats are fairly close to each other, making Item Level a good indicator of upgrades for the most part, since Agility is rather strong. The general Stat Ranking is outlined below, but you should always be simming upgrades.
Critical Strike > Mastery > Versatility/Haste
Agility: Increases attack power and damage.
Critical Strike: Grants a chance to critically strike, dealing double damage. Its interaction with Primal Fury allows your generator Crits to give you double Combo Points, doing a lot to improve the feel and flow of your rotation. Generally your best Stat.
Mastery: Increases the damage dealt by your Bleeds and Finishers.
Haste: Increases your energy generation and Bleed tick rate.
Versatility: A simple flat bonus to damage done and reduction to damage taken.
The best way to calculate stat priorities for your character is to "sim" your characterFind out how to sim
Feral is in a bit of a special situation in that there’s a Race whose Utility Racial provides us with a significant dps boost, that being Night Elf with Shadowmeld, making that Race far superior to alternatives.
Alliance: As discussed, Night Elf is by far the strongest option if you’re Alliance.
Horde: All Horde Races are very close, making it safe to pick based on personal preference, but Troll is very slightly ahead.
Cloak: Enchant Cloak - Fortified Avoidance is the general choice.
Rings: You should enchant your Rings based on your current best Secondary Stat, which will more often than not be Crit, therefore you should go for Enchant Ring - Tenet of Critical Strike.
Similarly to Ring Enchants, you will want to socket the Gem that gives you your current best Secondary Stat, that usually being Deadly Jewel Cluster.
Flask: Spectral Flask of Power
Potion: Potion of Spectral Agility
Rune: Veiled Augment Rune
Armor Kit: Heavy Desolate Armor Kit
Healing Potion: Spiritual Healing Potion