I'd suggest finding someone in your guild who has the tradeskill that makes the components you need for you leatherworking.
If you're not in a guild, try to make friends with someone who does the tradeskill you need and set up a trade agreement with them (ie- I give you X leather product for Y Alchemy/blacksmithing/etc product).
I'm just glad that I'm in a good guild that has enough crafters in it. We have all of the crafts covered and most of us are pretty close to the 300s, so no getting gouged on the AH for us. ^^
Now, on a sidenote....
http://wow.allakhazam.com/db/spell.html?wspell=7135 <--- Dark Leather pants
http://wow.allakhazam.com/spell.html?wspell=9072 <---Red whelp gloves
http://wow.allakhazam.com/db/spell.html?wspell=2166 <--- Toughened Leather armor
http://wow.allakhazam.com/spell.html?wspell=2158 <--- Fine leather boots
If you've got the patterns for these, you could always grind these as a lower cost to actually buying the elixirs and stones you need for the other things you can create. It may take more leather in the long run to get the needed skill ups, but at least you'll be making things that'll vendor at (mostly) break-even cost. But that's only if you farm your own leather and don't take into account the amount you could get for the same amount on the AH.
What is your level and class? If I knew that, I'd suggest a few places to grind creatures for the needed leather.
well, maybe these places will work for you....I only know Alliance, so, I apologize if you're Horde and this doesn't help you. :(
lv 1 - lv10 = Dun Morogh, for ruined scraps and light leather
lv 11 - 20ish = Loch Modan, There's a very nice islan in the lake, the one furthest south, that has these guys on it.
http://wow.allakhazam.com/db/mob.html?wmob=1693
If you're quick, you shouldn't get too many adds but be ready for some crazy spawning....I've had four spawn, one after the other in aggro range....Should be safe to stick to the fringes. Oh, yeah, this'll get you light and medium leather i think.
lv 20ish - lv 30ish = Wetlands, You'll want to grind these guys but be careful, adds and a few wandering slimes might get ya.
http://wow.allakhazam.com/db/mob.html?wmob=1042
They're great and die fairly quickly to an even level rogue^^ And they might drop one of the prized Whelpling pets for ya^^.
After that, I've just been wandering around, killing beasties as i see them. I wouldn't want to tell you to go to Hillsbrad Foothills, not with all the ganking that seems to be going on out there. But it was a good place in the 30s for me.
And when you hit the 40's, there's a nice area right south of Feathermoon in Feralas that has some lv40-41 wolves to grind for Heavy and Thick leather.
And right now, I'm wandering around Felwood at level 49-51 killing every wolf and bear I see. Most are lv 47-53 in the zone. Lower level ones in the south and progressing to the higher levels as you head north.
Just remember to watch your back out there from level 20ish on up. Way too much ganking going on, just gotta be aware of your surroundings.
Sorry for the lengthity of the post. I'm bored here at work.
One last piece of advice for ya, try to stick to making anything Orange or yellow, and move on once they hit green. And ignore that if your Orange or yellow recipes require expensive reagents like elixir's or buckle's or whatever^^.
Good luck