Hello! That sounds like an exciting trip to Poland. I'm glad to guide you.

Best Time to Visit:
The best time to visit these cities in Poland is between May to September when the weather is pleasant. However, if you're a fan of winter sports, December to February can also be a great time.

Route and Accessibility:
Your journey can start from the capital, Warsaw, which is well connected by flight to many parts of the world. From Warsaw, you can reach Kraków, Gdansk, and Wroclaw by train or bus. Alternatively, you can also choose domestic flights.

Accommodation and Booking:
All of these cities offer plenty of accommodation options, from budget hostels to luxury hotels. It's recommended to book your accommodation in advance via online platforms like Booking.com or Airbnb, especially during the peak tourist season.

Clothing and Essentials:
Pack according to the season. For summer, light clothing should suffice. However, do carry a raincoat or umbrella as rain showers can be unpredictable. For winter, heavy woolens, thermals, and water-resistant clothing are a must. Don’t forget comfortable walking shoes, a travel adapter, and possibly a portable WiFi device.

Health and Safety:
Poland is generally safe, but as with any other destination, you should be aware of your belongings and avoid remote areas at night. Always have a copy of your identity proof and travel insurance. Tap water is safe to drink, but if unsure, prefer bottled water. It's recommended to have EHIC (European Health Insurance Card) coverage.

Local Etiquette and Respect:
Polish people are generally formal and polite. When meeting someone for the first time, a firm handshake is typical. Tipping is appreciated in restaurants and taxis. Respect the laws, local customs and religious sites. Take care not to make jokes about Poland's WWII history, as it's a sensitive topic.