Ledaa has it right. A lot of the lower grade key mats can just go back to the npc store.. such as "blue diamond necklace gem" or "necklace of anguish chain." However, never EVER sell your basic mats to the npc store, no matter how desperate you get for adena. Players pretty much always give better prices.
Nonononono, do not get rid of basic mats ... trust me you'll miss that 800 bones and 300 iron ore and 200 varnish when you start crafting your own things :D
The following basic keymats you can sell to the NPCs; they're for no-grade crafts, and nobody uses those ...
<ul type="square">
Blue Diamond Necklace Gem
Boot Lining
Bow Shaft
Brandish Blade
Broadsword Blade
Cedar Staff Head
Composition Bow Shaft
Dirk Blade
Forest Bow Shaft
Hard Leather Gaiters Material
Hard Leather Shirt Pattern
Iron Hammer Head
Leather Gloves Lining
Leather Helmet Design
Leather Shoes Texture
Leather Stocking Pattern
Leather Tunic Pattern
Necklace of Anguish Chain
Necklace of Wisdom Chain
Piece Bone Breastplate Fragment
Piece Bone Gaiters Fragment
Short Spear Edge
Sword Breaker Edge
Sword of Reflection Blade
Willow Staff Head
I might have missed some ... ask your friendly local crafter when in doubt. :)
The other materials are usually worth more when sold to player shops, but you have to have a good grip on the current market prices. If you want to sell, try to sell in Giran - the "lowbie" places are usually full of people who're trying to get your mats for way below their market value (I've seen one with 150a for a single animal bone resp. 1500a for coarse bone powder yesterday - those materials are worth about 750-800a for the bone and 7500a-8000a for the powder on Teon currently). I'm running my own little "Buying all of the basic materials you have, for the current selling value -10%" business on Teon, which saves you the running to Giran and checking the prices yourself - but this needs a good amount of trust between me and my suppliers.
Your other alternative is to keep the mats. You'll need them later for crafting your own stuff, anyway.
If you decide to teleport to Giran (instead of, say, running there or putting a price-checking lvl3 toon there), two additional pieces of advice:
1. Don't port there directly. Port to each town on the way; that's way cheaper (Example: From Rune to Aden, teleport first to Oren, than to Aden - you'll pay 16900a instead of the 37000a of the direct route).
2. From Dion, port to Tanor Canyon or Beehive, then use a SoE to get to Giran (might involve a short walk, I'm not sure ...); on the way back, run the northern path back to Dion until you're in Dion territory, then use a SoE.