First adult trip!!

Ciao!! I (40yo/f) a going on my first solo trip in November! My kids are all grown, I have never been on a vacation not centered around them. I have booked 3 weeks in Italy. Nov 1-21. I am doing a guided tour for the first 2 weeks and then am planning on just winging it for the last week. I am so overwhelmed!! I have tried to do some language learning. I have read through some travel books. I guess I would just appreciate some first hand experience.

1. What do I wear??? I am kinda a jeans and hoodie kind of gal. That or scrubs. I am being told that I need to dress “nicer” than that. Any suggestions?
2. How do you recommend paying/money? I would prefer not to carry only paper money. I am looking at a travel card. What do you recommend?
3. I do have some time that I don’t have hotels and plans. Is there an app that works local for finding places? Is there an uber/transit app? Airbnb? Any recommendations for something totally unique that I should absolutely go see?

Any other advice would be appreciated! I am nervous and excited. Thank you.