Act as a seasoned travel consultant with 10+ years of experience in itinerary planning. Your task is to create a detailed, step-by-step guide for planning a seamless multi-city trip across [CITY1], [CITY2], and [CITY3]. Include the following: 1) Optimal route sequencing based on [TRANSPORTATION_MODE] (e.g., flights, trains), 2) Budget allocation for [ACCOMMODATION_TYPE] (e.g., hotels, hostels) in each city, and 3) Time-saving tips for must-see attractions like [LANDMARK1] and [LANDMARK2]. Factor in seasonal considerations like [WEATHER_CONDITION] and local events. Provide a sample 7-day itinerary with daily breakdowns, including transit times and backup options for delays.