What resolution do you game at and is this for modern AAA games? At 1080p I’d expect your cpu to be a limiting factor paired with a 2060 in modern AAA games. Quad cores are entry level cpu’s In these games. Also you would want 16gb RAM.
I suppose I am saying a 2060 will be unbalanced in your system. However if you plan to upgrade the rest then starting with the gpu is a good place.