if you want XP it depends. if your looking for 1000 or things like that go to marleybone. mooshu is more 2000s. there are hardly any random quests in dragonspyre. if your looking for XP best of luck in mooshu
I've leveled 4 wizards up to Grandmaster, here's my advice:
1. Pick the quest that gives you the most XP. Work on it.
2. Skip quests that do not move the storyline ahead. Generally speaking, it's hard to tell which quests are "important" and which ones are "extra". However, there are indications. For example, in Marleybone, there are several quests which obviously have no connection to the storyline. As a rule, if the NPC asks you to take a message to someone else, run to a shop or has a "personal" issue, it's a side quest.
3. When it comes time to kill off some monsters, choose your location carefully. Switch to a crowded realm and look for other players who are killing the same monsters. When you enter the battle, make sure that the next enemy headed toward the battle circle is the one you've been instructed to kill. If you are lucky, you'll find other people working on the same quests, and you'll make some new friends.
4. Mark your location frequently. For example, in Krok, you are often instructed to run back and forth. So, when you talk to an NPC that sends you on a goose chase, mark his/her location. Then, after you find the person you are supposed to talk to, you can just port back to the NPC that gave you the mission. Saves loads of travel time.
5. NEVER port to a world that you don't have quests in just to "kill stuff for XP". It's the least efficient way to gain experience. Even the most basic quests for a novice in Wizard City are worth more than killing a monster in Dragonspyre.