Sincere doubt about upgrade, what should I do in this configuration?

Personally, my config is: Ryzen 5 3600 B450 Machenist 16gb Asgard Rx 6600

I'm not sure what to change, I know I have a bottleneck because the mobo is pci 3.0, and the gpu and processor are 4.0. However, I don't have Crtz if changing the mobo would be the most ideal, perhaps a new gpu? I'm going to stay on the am4 for a while yet and in the future I would like to add a Ryzen 7 5600 to go with a 5060