In order to attain the entire Beastmaster set (Tier 0.5) you must first get the entire Beaststalker set. Once you have gotten all of the Beaststalker set, then follow these instructions to attain the entire Beastmaster set.

To upgrade the Tier 0 (Beaststalker) set to Tier 0.5:

Bracers

* 20gold
* 15 Winterspring Blood Sample (Thottbot) (Alliance)
* 15 Silithus Venom Sample (Thottbot) (Horde)

Belt & Gloves

* 1 Delicate Arcanite Converter
* 4 Greater Eternal Essence
* 10 Stonescale Oil
* 80/90gold
o 40gold to Mux Manascrambler
o 40/50gold to buy a Quest Item: Fel Elemental Rod
* Extra Goblin Rocket Fuel as needed

Shoulders, Boots, & Pants

* 3 Dark Iron Bars (Thottbot)
* 3 Mooncloth (Thottbot)
* 20 Enchanted Leather (Thottbot)
* 4 Cured Rugged Hide (Thottbot)
* 8 Large Brilliant Shard (Thottbot)
* 4 Dark Runes (Thottbot)

Helm & Chest

* 120gold to buy a Hallowed Brazier (Requires Argent Dawn - Honored)
* 1 Flask of Supreme Power (Thottbot)
* The following items are required to Summon the Duke of Cynders. You must also be Friendly with Cenarion Hold
o 1 Twilight Trappings Set:
+ 1 Twilight Cultist Robe (Thottbot)
+ 1 Twilight Cultist Mantle (Thottbot)
+ 1 Twilight Cultist Cowl (Thottbot)
o 1 Twilight Cultist Medallion of Station (Thottbot)
+ 1 Large Brilliant Shard
+ 3 Abyssal Crest (Thottbot)
# You can either buy them at the Auction House or summon 3 Abyssal Templars at a Wind stone in Silithus, which will require 3 Twilight Trappings sets.
o 1 Signet of Beckoning: Fire (or luck) (Thottbot)
+ 1 Dark Rune
+ 5 Firebloom
Total gold: 220gold (Costs for buying materials excluded)

Note: As you're level 60 when you become able to do these quests, a little of the gold you spend will be returned as quest rewards instead of XP. Calculated 611gold required approximately to do this quest, about 700gold on a more expensive server and about 40gold refunded from quest experience to gold at lvl 60.

Hope that helps.

You don't necessarily have to have a full Tier 0 set to start updating to Tier 0.5. The first quest only deals with the bracers, so you can complete the first part by only owning the bracers.