Much like reading a chapter book, Wizard101 is sequential game play (before you move to level 2 you must complete level 1). Even if you have purchased a Membership you must first complete all of the quests in one world to be able to move on to the next.
The same thing goes for access to some of the streets or areas within a world. For instance, when you've successfully completed the quests for Wizard City you will be given a quest to enter into the next world, Krokotopia. Once you have earned your own access there, as long as you have a Membership or have purchased the zone with Crowns, you will be able to enter that zone with your character. Simply put, complete the tasks you are given and don't concern yourself with your level or the level/advancement of other players.
You need to beat lord nightshade then when you talk to Ambrose he will give you a spiral key and send you to bartleby bartleby will show you how to go to different worlds than he will open and inside him is a world gate also if you have a castle you could use the one there like I always do
You have to complete Unicorn Way, Triton Avenue, (membership streets) Firecat Alley, and Cyclops Lane. Then Headmaster Ambrose will give you the Quest Look of Horror then you defeat 2 bosses then you go to Night Side and talk to Dworgon and then you go back to headmaster and then you go to Krokotopia!