Gear
Survival is very dependent on Agility in the sense that the more Agility you have, the more it will benefit you (obviously). This is due to the Expose Weakness talent. Currently in my raid gear I have 1879 Agility unbuffed. Raid buffed, this can jump close to 2400. Expose Weakness offers 500-700 Attack Power when it's up. This is HUGE.
Survival is also very Crit-Based. Do not neglect Crit rating from gear! this is often a huge mistake I (and many other Hunters I have seen) make in game.
Gems
Always gem for Agility, except when you have your best set bonus (I.E. 32 AP, 12 AP) in which case you place a +10 to stats gem which would also take care of your Meta Gem if you're using the correct one.
Red Gems
Delicate Cardinal Ruby: +20 agi
Delicate Scarlet Ruby: +16 agi
Orange Gems
Glinting Flawless Ametrine: +10 agi +10 hit
Deadly Flawless Ametrine: +10 agi +10 crit
Glinting Noble Topaz: +8 agi +8 hit
Deadly Noble Topaz: +8 agi +8 crit
Purple Gems
Shifting Dreadstone: +10 agi +15 stam
Shifting Twilight Opal: +8 agi +12 stam
Green Gems
Vivid Eye of Zul: +10 hit +15 stam
Jagged Eye of Zul: +10 crit +15 stam
Prismatic Gems
Nightmare Tear: +10 stats
Enchanted Tear: +6 stats