To make the most of your day, consider purchasing the Park-to-Park admission ticket, which allows you to hop between the two parts of the Wizarding World. The cost of the ticket is $170. Trains depart from King's Cross Station and Hogsmeade Station every 10 minutes. Travel time between the two parts of Harry Potter World is approximately 20 minutes.
If you have more time, you can spend an entire day exploring both Diagon Alley and Hogsmeade. Alternatively, if you have less time, consider skipping one of the locations and spending more time at the other. Also, don't forget to check wait times for the rides to maximize your experience.