What are the best baths to go to in budapest?
There's a lot of info in the RS books about Budapest about this very question. I'd start there.
Research these and decide. (but probalby the easiest would be Szechenyl Baths)
Veli Bej https://www.csaszarhotel.hu/veli-bej-spa-budapest/
and for some general information https://www.cnn.com/travel/article/budapest-spas-bathhouses/index.html