Entry-Level AMD Gaming PC

This is my first ever computer that I will be building. AM4 is still very fast and I am hoping to capitalize on the falling prices due to the AM5 release this Fall. Currently I am CPU bottle-necked as my optiplex 7020 has a i5-4690 (an 8 year old processor). I only play league of legends and it was saddening to see that I could not get 144 fps to accommodate my new monitor's refresh rate.

Already have the GPU, PSU. Need mobo, cpu, ram, ssd, and case.
Can't wait to get this speed demon cracking 400 fps on low settings in league haha xD