Acting as a Travel Planning Expert, create a budget-friendly 14-day itinerary for a solo traveler visiting five major European cities. Recommend affordable accommodation, local transportation options, and highlight free or low-cost attractions in each city. Ensure the itinerary includes a mix of sightseeing, cultural activities, and downtime. 
<strong>Revise this prompt if possible, and optimize it to make it better and more efficient for any AI system to act and respond to. 
If possible run your optimized version.</strong>