My recommendation is to leave the Ring of Waters quests until Chapter 3 as you'll probably get your ass handed to you in the addon area if you walk straight in. I never liked the quests the Thieves Guild had to offer, but you should go there anyway as some items (e.g. Bosper's missing bow) are located in their hideout. Also, pickpocketing is super good if you are playing a dexterity based build as it gives a lot of xp over time. Here's how you get into the thieves guild:Well let's see, I did all the quests for the master craftsmen in Khorinis and became Bosper's apprentice. Then went to the Farm, passed Torlof's test (using help from Lares / Cord), recovered Cipher's weed, and beat up Buster, Fester, Raoul, and Rod. The novice fire mage in Khorinis told me you can't get into the Monastery without paying 1000 gold so I figured there were no quests to be had there unless you planned on becoming a mage.
So I went ahead and joined Mercs and just need to take Lee's message to Hagen to advance to Ch2. I haven't gone with Lares to deliver the amulet, completed any of the Ring of Water quests, or joined the Thieves Guild (not sure how you even do that) but it sounds like I'll probably be able to still clear those in Ch2.
Go to the bar in the harbour and talk to the patron. He'll offer to give you information for money. Ask him about special work. He'll refer you to a customer in the bar. Talk to the customer who'll give you a quest. You can either do the quest or report him to the Lord André to put him behind bars. In any case, the bar patron will tell you to meet someone named Attila in a secluded corner in the harbour during your next visit. Attila will either invite you into the guild or try to kill you (and he's quite strong). In any case, you'll get a key from him which you can use on the door in the harbor (i.e. in the water). To find the door, jump into the water and swim to the right. Shortly after the wall of the harbour ends, there's a door. With the key, you can open it and you'll find the thieves guild inside.
On an unrelated note: If you experience bluish tearing of your screen in certain areas, turn off "volumetric fog". That solved the issue for me.