Thief: Deadly Shadows

Each shop only has one of the four elemental arrows:

South Quarter AKA Well Equiped Thief: Water Arrows.
StoneMarket Proper AKA Marla: Moss Arrows.
Docks AKA The Undercurrent: Fire Arrows.
Old Quarter: Gas Arrows.

Certain fences only take certain loot. Here are some examples:
Docks fence, AKA Dalia: Artwork & Gems.
South Quarter fence, AKA Heartless Perry: Gems & Metal.
Stonemarket fence AKA Blackmarket Bertha: Gems & Metal.

For the Hammerite and Pagan side-missions, you normally can only fulfill them for one faction or the other. The Fort Ironwood graveyard mission can be glitched slightly to gain the benefits of boths sides (although the faction meter only aggregates for one faction only).

You get the Fort Ironwood graveyard side-mission after clearing the Clocktower mission and getting the Keeper Enforcers on Garrett's tail in the Old Quarter. Head to Fort Ironwood (it's easier if the Hammerites are already allied with Garrett) and enter the graveyard behind it. There's a Pagan Cornerstone in the graveyard that can be "mossed"; find it near one of the columns (pagan cornerstones only appear on 90 degree corners) by the back wall of Fort Ironwood. This will accomplish the Pagan's part of the side-mission.

Assuming you did not go past the archway under Ramien's place in Old Quarter (leads to the Docks and Shalebridge Asylum) before doing the above, you can go there now and locate a small sewer tunnel where a Pagan Shaman would normally be. If the game glitched, the shaman would not be there, but his wand (worth $200) will be floating in mid-air. Grab it be a bit richer. You also get the benefit of the Pagan cemetary ... there'll be an earth crystal near the pagan cornerstone each following night (or the same night, if you reload the Old Quarter map).

You can get free water arrows in the training mission (which carries over to your subsequent missions) by waiting by the douse the torch exercise for water crystals to keep respawning. Before you leave the Blue Heron Inn forever, you may want to take your fill of 25 water arrows, which will go a long way in helping you keep shopping costs down.

When you first arrive at the docks, go towards the store. Stop immediately after you pass the Quarantine gate. There is a box in front of you. Destroy it. Go down the ladder and follow the stairs.