More salvage questions...

should i be using expert salvage kits on items like ash fiend trappings, axe fiend armor, stalker armor, etc?

Sure, if you can afford it.
Expert kits always do a better job than regular ones. Giving you either more of the material or rarer materials, but early in the game they're just too expensive.

Put quite bluntly:

No.

Unless you have a steady source of income or some way of making massive amounts of money at your word, don't use Xpert Kits on junk. It isn't worth it in the long run.

so what do i use expert kits on? just purple and yellow items?

Anything that will give you a rune or upgrade usually. Or if you're trying to get a particular rare crafting material (ie: fur squares from enemy hides).

When you compare the cost per expert salvage, to what you get in common crafting materials, you typically want to save them for the important stuff.

I just use my expert kit to extract runes and upgrade components. Otherwise I use regular kits to make materials and if I need something like silk or steel or whatever, I go to a materials' trader.

Expert kits cost 400 vs. regular at 100, if that is too expensive, I am not sure what you are doing. In a typical run, I collect anywhere from 100 to 300 gp worth of items outside of asclon and when I say run, I am not talking farming, I mean doing quests or missions.

Also for me, a 25 use expert kit lasts 3 or 4 runs. So in a nutshell, I suggest once you can start buying expert kits, get them. With expert kits you usually (not always) get more of the common crafting item out of the salvagable item plus you have a shot at getting rare crafting materials which you can not not extract with a regular item and yes I have gotten rare materials from items just outside of Ascalon. Al least thats my thought.

I only use Expert kits on items that contain a rune (shown by the little window that pops up when you ID it) or items that I think I could salvage a weapon upgrade from. What I mean is this;

Sometimes you get a blue (unidentified) item, and when you ID it, let's use a bow for the sake of argument, it will show that the bow does poison damage, but no special window will pop up telling you there is something rare inside. It just shows that the bow will do poison damage. So, when you use a salvage kit on it, you'll get between 1-5 wood planks. Use an expert Salvage Kit and you'll get 5-? wood planks, 80% of the time, and the other 20% you'll salvage a 'bow string of poison damage' or whatever.

So the rule of thumb is; only use salvage kits on items that you think you can get something special out of. Don't bother with trappings/gears/skins/hides/armours/etc. Use regular salvage kits, or trade them to materials traders (trading 4 Charr Hides gets you a Fur Square in Ascalon, for example).

I make money pretty quick now, so I tend to use my expert salvage kit on every single blue/purple/gold item I find. If I see a weapon/item drop, and it's white, I typically just leave it.

Using expert salvage kits on all sorts of seemingly useless blue weapons has filled my bank-storage with a metric f*ckton of weapon upgrade components (hilts, shafts, bowstrings, etc).