I'm trying to find some ebony armor, which is easy at my current level (lvl 18), but I've already cleared no less than three marauder dungeons and still no gauntlets to be seen.

If you've got a lot of gold and don't mind spending it, head to the Mystic Emporium.

http://www.uesp.net/wiki/Oblivion:Hands_of_the_Atronach#Hands_of_the_Atronach

Maybe Umbra will let you wear her Ebony Gauntlets. If you ask politely.