The most famous and most affordable thing in Hangzhou is the West Lake. Many attractions are free, such as Su Causeway, Bai Causeway, Beishan Road, Broken Bridge, etc. You can enjoy the surrounding scenery while walking, and you will pass by many free attractions, such as Sing the Orioles in the Willows and Huagang View.
Fish, as well as the former residences of celebrities, etc.
Some tickets are also very cheap, depending on your interests.
If you want to experience special snacks, you can walk from West Lake to Qinghefang and Gaoyinxiang Food Street. There are restaurants on each street, all of which are authentic Hangzhou cuisine.