The levelling guide is divided into 4 parts:
1-150 with Low Mats(vendor), Max Profit(DE/AH), What I Did
150-205 with Low Mats and Nice Profit, Max profit(AH)
205-250 with Max Profit(Elemental), Dragonscale and Tribal
250-300 with Max Profit(DE/AH)

1-150 Low Mats
Mats needed: 275 Light Leather, 20 Light Hides, 25 Medium Hides

1-35
35 Light Armour Kit - 35 Light Leather

35-55
20 Cured Light Hide - 20 Light Hide

55-85
30 Embossed Leather Gloves - 90 Light Leather

85-100
15 Fine Leather Belt - 90 Light Leather

100-120+
25 Cured Medium Hide - 25 Medium Hide

120-125
10 Fine Leather Belt - 60 Light Leather

125-150
25 Dark Leather Belt - 25 Fine Leather Belts, 25 Cured Medium Hides

1-150 Max Profit
Mats needed: 385 Light Leather, 20 Light Hides, 25 Medium Hides

1-35
35 Light Armour Kit - 35 Light Leather

35-55
20 Cured Light Hide - 20 Light Hide

55-80
25 Embossed Leather Boots(DE) - 200 Light Leather

80-85
5 Fine Leather Belt - 30 Light Leather

85-90
5 Fine Leather Tunic - 30 Light Leather, 15 Cured Light Hide

90-100
10 Fine Leather Belt - 60 Light Leather

100-(120+)
25 Cured Medium Hide - 25 Medium Hide

(120+)-125
10 Fine Leather Belt - 60 Light Leather

125-150
25 Dark Leather Belt - 25 Fine Leather Belts, 25 Cured Medium Hides

1-150 What I Did (which might give better profit than Max profit, but it required some world drop recipes)
Mats needed: 78 Ruined Leather Scraps, 259 Light Leather, 35 Light Hides, 25 Medium Hides

1-27
26 Light Leather - 78 Ruined Leather Scraps

27-35
10 Light Armour Kit - 10 Light Leather

35-66
35 Cured Light Hide - 35 Light Hide

66-75
9 Rugged Leather Pants - 45 Light Leather

75-80
5 Fine Leather Gloves - 20 Light Leather, 5 Cured Light Hide

80-85
5 Fine Leather Belt - 30 Light Leather

85-95
10 Fine Leather Tunic - 60 Light Leather 30 Cured Light Hide

95-105
10 Fine Leather Belt - 60 Light Leather

105-120
25 Cured Medium Hide - 25 Medium Hide

120-125
10 Fine Leather Belt - 60 Light Leather

125-150
25 Dark Leather Belt - 25 Fine Leather Belts 25 Cured Medium Hide

150-205 Low Mats with nice profit
Mats needed: 410-430 Heavy Leather, 10 Heavy Hides, 20-40 Bolts of Silk Cloth(80-160 Silk Cloth), 10 Iron Buckles

150-160
10 Cured Heavy Hide - 10 Heavy Hide

160-170
10 Heavy Armour Kit - 50 Heavy Leather

170-180
10 Dusky Leather Leggings - 100 Heavy Leather

170-180 (If you don’t have Dusky Leather Leggings Pattern)
10 Guardian Pants - 120 Heavy Leather 20 Bolts of Silk Cloth

180-190
10 Barbaric Shoulders - 80 Heavy Leather, 10 Cured Heavy Hide

190-195
5 Dusky Bracers - 80 Heavy Leather

195-205
10 Dusky Belt - 100 Heavy Leather, 20 Bolts of Silk Cloth, 10 Iron Buckle

150-205 Max Profit
Mats needed: 435-450 Heavy Leather, 10 Heavy Hide, 20 Bolts of Silk Cloth(80 Silk Cloth), 10 Iron Buckles

150-160
Cured Heavy Hide - 10 Heavy Hide

160-165 Here you have 3 choices. Hillman’s Cloak is used in Alliance quest, can sell. Barbaric Bracers will give nice profit if you have mats to make it, and Heavy Armour Kit is just a filler for horde without mats for Barbaric Bracers.
5 Hillsman’s Cloak - 25 Heavy Leather
5 Heavy Armour Kit - 25 Heavy Leather
5 Barbaric Bracers - 40 Heavy Leather, 10 Cured Heavy Hide, 20 Small Lustrous Pearls, 5 Raptor Hides, 20 Large fangs

165-180
15 Dusky Leather Leggings - 150 Heavy Leather

180-190
10 Barbaric Shoulders - 80 Heavy Leather, 10 Cured Heavy Hide

190-195
5 Dusky Bracers - 80 Heavy Leather

195-205
10 Dusky Belt - 100 Heavy Leather, 20 Bolts of Silk Cloth, 10 Iron Buckle

For more details about Leatherworking Specialisation, read this:

http://www.wowgoldwiki.com/professions/leatherworking-specialisation.html

When it says Nightscape Headband/Tunic, it means you can choose. Tunics use 2 more Thick leather than Headbands, so if you’re only disenchanting Headbands is the best, while if you’re putting on AH a mix is better.

205-250 Max Profit (also Elemental)
Mats needed: 405-455 Thick Leather, (2 Hearts of Fire, 2 Globes of Water, 2 Cores of Earth, and 2 Breaths of Wind)

205-230
25 Nightscape Headband/Tunic - 125-175 Thick Leather

230-250
20 Nightscape Pants - 280 Thick Leather

205-250 Dragonscale
Mats needed: 441-483 Thick Leather, 40 Scorpid Scale, 10 Worn Dragonscale

205-226
21 Nightscape Headband/Tunic - 105-147 Thick Leather

226-228
2 Tough Scorpid Breastplate - 24 Thick Leather, 24 Scorpid Scale

228-230
2 Tough Scorpid Gloves - 12 Thick Leather, 16 Scorpid Scale

230-250
20 Nightscape Pants - 280 Thick Leather

205-250 Tribal
Mats needed: 427-449 Thick Leather, 112 Turtle Scale, 11 Wildvine, 2 Cured Thick Hide

205-211
6 Thick Armour Kit - 30 Thick Leather

211-222
11 Nightscape Headband/Tunic - 55-77 Thick Leather

222-224
2 Turtle Scale Gloves - 12 Thick Leather, 16 Turtle Scale

224-226
2 Turtle Scale Breastplate - 12 Thick Leather, 24 Turtle Scale

226-228
2 Turtle Scale Bracers - 16 Thick Leather, 24 Turtle Scale

228-229
1 Wild Leather Vest - 12 Thick Leather, 2 Wildvine

229-230
1 Wild Leather Helmet - 10 Thick Leather, 2 Wildvine

230-232
2 Turtle Scale Helm - 28 Thick Leather, 48 Turtle Scale

232-250
18 Nightscape Pants - 252 Thick Leather

250-300
Mats needed: 160 Thick Leather, 470 Rugged Leather

250-260
10 Nightscape Boots - 160 Thick Leather

260-270
10 Wicked Leather Gauntlets - 80 Rugged Leather

270-285
15 Wicked Leather Bracers - 180 Rugged Leather

285-300
15 Wicked Leather Headband - 210 Rugged Leather

Recipes:
Rugged Leather Pants http://www.thottbot.com/?i=1690
Fine Leather Gloves http://www.thottbot.com/?i=1425
Barbaric Bracers http://www.thottbot.com/?i=40382
Dusky Leather Leggings http://www.thottbot.com/?i=12602
Turtle Scale Gloves http://www.thottbot.com/?i=14318
Tough Scorpid Breastplate http://www.thottbot.com/?i=10512
Tough Scorpid Gloves http://www.thottbot.com/?i=11970
Wild Leather Vest http://www.thottbot.com/?i=10314
Wild Leather Helmet http://www.thottbot.com/?i=13899
Wicked Leather Gauntlets http://www.thottbot.com/?i=11493
Wicked Leather Bracers http://www.thottbot.com/?i=15695
Wicked Leather Headband http://www.thottbot.com/?i=14993

300-310
Knothide Leather (5 x Knothide Leather Scraps) x 20 = 100 x Knothide Leather Scraps
N.B. make as many as it takes to get to 310. Your going to need around 725 Knothide leather, so you may as well get the skill up points for this.

310-320
Wild Draenish Gloves (9 x Knothide Leather, 3 x Rune Thread) x 10

320-325
Thick Draenic Boots (10 x Knothide Leather, 3 x Rune Thread) x 5

325-335
Heavy Knothide Leather (5 x Knothide Leather) x 80
Your going to need 80 later on, so get the skill up points for making it.

335-340
Thick Draenic Vest (14 x Knothide Leather, 3 x Rune Thread) x 5

340-355
Felscale Breastplate (14 x Knothide Leather, 3 x Fel Scales, 3 x Rune Thread) x 15

355-365
Welcome to the Clefthoof Leather grind. Your going to hate Nagrand by the time your finished leveling to 375.
You need to be Friendly with Cenarion Expedition for the next part:
Heavy Clefthoof Boots (4 x Heavy Knothide Leather, 20 x Thick Clefthoof Leather, 4 x Primal Earth, 2 x Rune Thread) x 10

365-375
Drums of Battle (6 x Heavy Knothide Leather, 4 x Thick Clefthoof Leather) x 20
Requires Sha’tar Honoured rep

Approximate Materials Required

100 x Knothide Leather Scraps
380 x Knothide Leather
160 x Heavy Knothide Leather
125 x Rune Thread
45 x Fel Scales
280 x Thick Clefthoof Leather
40 x Primal Earth