The items you steal and loot from chests and stores will always be gear of your current character level. If you want to level clothier this way, continue leveling your character and the items you steal will always be high enough to level your crafting skill unless you level your skill far past the gear you can currently wear. If you play dominion, there is a shop in vulkhel guard just south of the blacksmith and clothier stations that has a large stock of stealable armor. This is a decent place to start. Most of the larger cities have weapon/armor shops you can steal from in this same way and then just deconstruct your hauls.