dragon-age-guide - Merchants and Goods

I made a list of all the items I purchased throughout the game.
I also bought all armor upgrades for those companions I didn't use.

Merchants Act 1:

Docks, Shady Merchant: Cruel Dagger (+6 damage vs. humans makes it a great dagger. You'll be fighting a lot of them during act 1.)

Lowtown, Lirene's Fereldan Imports: Tarnished Dagger

Lowtown, Weaponsmith: Thrice-Bound (note: only necessary if you decide to play without Varric in your group to disarm and open stuff!)

High Town, Jean Luc: Backpack

Lowtown, Apparal Shop: Backpack, Varric Armor Upgrade

Gallows, Mage Goods: The Turncoat's Walking Stick (redundant if you use Staff of Parlathan)

Lowtown, Trinkets Emporium: Amulet of Influence

Lowtown, Armorer: Aveline Armor Upgrade

Lowtown, Lirene's Fereldan Imports: Design: Rune of Frost

The Dark Emporium: 4x Maker's Sigh Potion, Sturdy Belt

The Gallows, Weapons Shop: Rune of Fire (I put one in Bianca)

The Gallows, Mage Goods: Rune of Lightning Warding (before entering the Deep Roads put this one in Varric's armor)

Hightown, Hubert: Tome of Technique

Docks (Night), disused Passage, Bonny Lem: Enchanted Silverite Chain, Staff of the Primal Order, Thunderpucker's Fist (only if Aveline is a full member of your group)

Merchants Act 2:

Hightown, Jean Luc: Backpack, Armor Upgrades for Merrill, Fenris, Isabela

Gallows, Mage Goods: Backpack, Armor Upgrade Anders

Lowtown, Armor Merchant: Armor Upgrade for Aveline

Lowtown, Trinket's Emporium: Greater Tome of the Mortal Vessel

Lowtown, Apparel Shop: Isabela Armor Upgrade

Lowtown, Lirene's Fereldan Imports: Anders Armor Upgrade, Tear of Ferelden

Sundermount, Master Ilen's Shop: Tome of Technique, Merrill Armor Upgrade

The Dark Emporium: Elixir of Physical Technique, Greater Elixir of the Mortal Vessel, Dull Brass Amulet, The Fallen Star

Other interesting trinkets:

Etched Ring of the Twins
perfect for a tanking 2H Warrior. But unless you want to go for maximal critical damage not really worth the mony for our rogue.

Puzzle Ring of the Black Fox
Also way too expensive in my opinion.
Bonus to lockpicking is useless because you need to disarm traps, too.

Stealth Boots
Good: Great boost for stats and critical damage.
Bad: Expensive, erases your set bonus (= -3 Dexterity)

Elixir of Arcane Technique
Grants one ability for a mage, available at Black Emporium.

Merchants Act 3:

Hightown, Jean Luc: Backpack

Hightown, Korval's Blade: Qunari Sword, Tome of Arcane Vessel (+3 attribute points for Hawke)

The Gallows, Weapon Shop: Qunari Sword

Lowtown, Weaponsmithy: Qunari Sword

Docks, Bonny Lem: Four-Fingered Eddie's Lucky Talisman (very expensive, but I had coin to spare, so I bought it for Varric)

The Wounded Coast, Magnus's Wares: Seven Deadly Cinch