Quen is in any thieves guild. Do her quests to, I think, thieves guild 2. Then when the board next to Keri opens (it's after a specific quest in the main story), these infinitely repeatable quests are an easy way to level.

Keri's quests involve one of three tasks: 30 pickpockets, 3 lockbox raids or delivering 3 laundered items of a specific category to an npc. The first repeatable is picking pockets, and that's mandatory. After completing this, you can drop and pick up a new quest over and over until you get the one you want. Most people dislike pockpocketing...so the chests tend to be easiest. Get one of these, then look for safes. Use the maps if you don't know where they spawn:

http://roguesfolio.tumblr.com/post/117474683047/velyn-harbor-bustles-with-abecean-trade-picaroons

The daily heists are even better...but you only get one a day and they're hard for unsneaky toons. These open after the second or third main quest (where you go find velsa). A quest will spawn in the den over between the fence and back entrance. Follow this and it'll unlock dailies, which are worth about 4 repeatables in terms of leveloimg.