What do I upgrade?

Right now I during the Christmas season I want to buy some new PC parts. My current specs are a 1660 super, Ryzen 5 3600x, 16gb of ram, 1tb of storage, I think 650w PSU (need to check), and a B450 Arous motherboard. I have around $500-$600 to spend. I am currently playing rust I just want to know what GPU and CPU's would help improve fps as I'm pooping out 40-50 frames on large servers