For a thief of your caliber, you're looking at light leather or plain cloth. however, as we progress through the RP (and I am talking about at least a few months in RP time), your characters will become stronger that they'll be able to don light chainmail or even brigandines. quilted armor is actually quite thick and cumbersome, restricting movements. there are, however, special cloaks specifically designed for thieves that are lighter and react to their environment's lighting. The lighter it is, the cloak almost seems to help the user vanish into the environment when they unhook it and completely unfold it. At night, the thief seems to almost disappear in the darkness. Still visible, but unseen by those none expecting. In fact, 80% of Ghost sightings throughout this world are actually thieves with the money to get a hold on these expensive capes. However, like all capes, they do wear down over a long period of time.