Planning a solo grad trip to Europe!!

Hi everyone! Im planning this trip for early June to early August. Ive never traveled alone before only with my older brother in the US. Safety is my biggest concern and #1 priority. I was planning to spend most of my time in Italy but considering the amount of time I have I would love to venture out to the South of France, Switzerland, Spain, or maybe Lisbon?

I need recommendations for specific places in those areas along with hostels/hotel, sightseeings, restaurants, and more info on traveling between each country, would train or flights be easier?

Essentially, Im looking for an itinerary anyone could share from their past travels to multiple or one city!! I love the beach, museums, architecture, nature, meeting new people, and thrift shopping!

Any tips/ideas are welcome!!