Good, now that you have the tower, you now have a source of infinite money and potions, thanks to your runners in the throne room (If you can afford to, equip them with better gear. If you're having trouble with ingredients or potions, only worry about outfitting the Plant-gatherer first.
To ACTUALLY answer your question, in the back of the throne room is an elevator to your private quarters, which has a waypoint shrine. Take it to Orobas Fjords. Even if you never visited that shrine, it will show up now. That's the only place available to level up in which is safe. You'll need to fly to a teleporter to get into a fort to shut off the anti-dragon barriers.
