I had a necklace of minor barter that was at 12%, I disenchanted it a silver necklace for 38% but when I tried it took the Gem and necklace but didnt show up, maybe it only works on Gold? ..... I just thought of that im going to try it .

Yep it only works on gold necklaces, I thought the last time I had 38% but I guess not this time it fluctuated to 21% .

The type of necklace makes no difference. If an enchantment works on a gold necklace, it will work on any necklace. The effect is tied directly to the necklace and not the material it's made from.

The strength of the effect is based on your enchanting skill, perks and the size of the soul gem. A grand soul gem filled with a grand soul will make the strongest enchantment effects.

The UESP has been the pinnacle of TES info for years, now. I'll place the links below to aid in explaining better than I can.

http://www.uesp.net/wiki/Skyrim:Fortify_Barter

http://www.uesp.net/wiki/Skyrim:Enchanting

http://www.uesp.net/wiki/Skyrim:Enchanting_Effects

possible something changed because I tried enchanting a silver necklaces and neither worked on but a gold one finally worked and at the same level .

There are a couple mods that change the % an enchant will be based on the type of jewelry used... crafting over haul, plus Immersive Jewelry. ..

A fire enchant will work better on xxx metal with zzz gems than another combination. If you have those type of mods, of course.

Vanilla enchanting I can coax the Barter level to 28% with a good potion. (25% is not difficult)

Any necklace as SC pointed out....don't forget to name it something so you don't accidentally sell it in hasty trading.

Thanks for pointing that out Rick I always forget to name the items .