This will help in finding items that you need. If they are not there or there isn't enough of an item. Buy everything, sleep for a week then go back.
Need: Regal Purple Dye
Where to get: Traveling Dye Trader/Clothing Trader (Fairfax Garden)
Economy Rating: *****
Reward: Brodican Mace
Need: Crucible Peanuts (x2)
Where to get: Crucible Food Trader
Economy Rating: ****
Reward: Chasm Outfit
Need: Crunchy Chick (x3)
Where to get: Food/Fish Trader (Westcliff/Bloodstone)
Economy Rating: *
Reward: Wretcher’s Blade
Need: Lute (x2)
Where to get: General Store
Economy Rating: *
Reward: Axe of Disharmony
Need: Monk Robe (x1)
Where to get: Oakfield Clothing Stall
Economy Rating: ***
Reward: Judge’s Steel
Need: Murgo’s Big Book of Trading (x2)
Where to get: Bowerstone Bookstore
Economy Rating: *
Reward: Brodican Warrior Queen Outfit
Need: Pure Experience Extract (x1)
Where to get: Bowerstone Market/Potion Trader (Fairfax Gardens)
Economy Rating: *****
Reward: Hal’s Rifle
Need: Diamond (x1)
Where to get: Bowerstone Market Jeweler
Economy Rating: *****
Reward: Staff of Wrath
Need: Eternal Love Ring (x1)
Where to get: Bowerstone Market Jeweler
Economy Rating: *****
Reward: Greaser Wig
Need: Marriage and How To Survive It (x1)
Where to get: Bowerstone Market Bookstore
Economy Rating: *
Reward: Knothole Skirt
Need: Pretty Necklace (x1)
Where to get: Jeweler/ Gift Trader
Economy Rating: ***
Reward: Black Wheel Gang Outfit
Need: Puny Carrot (x2)
Where to get: Bowerstone Old Town (Food Stall)
Economy Rating: **
Reward: Assassin Outfit
Need: Table Wine (x2)
Where to get: Bar
Economy Rating: ***
Reward: Cascading Hair
*note, I do not take credit for this...this list was posted here:
http://www.xbox360achievements.org/game/fable-2/guide/