After running a campaign in Monte Cook’s Ptolus : City by the Spire for 3 years, I wanted to give you some advice on how to start your game in this huge, urban metropolis.

First, you need the book. Second, you need this website.

Player’s Guide to Ptolus: https://ptol.us/a-players-guide-to-ptolus/
You can download the PDF, or read the entire contents in a mobile friendly format on your phone/tablet/device.

My #1 Advice for DMs/GMs and Players unfamiliar with Ptolus: Start the campaign with the PCs not knowing much of anything about Ptolus. Start them as outsiders to the City by the Spire and let them learn as you move through the city for the first time.