Think the best setup is need to get motherboard which supports multiple gpu 6+
That way you wont waste your money, just building a CPU rig.
I would go for Biostar TB350 and Ryzen9 3900x
Add some Nvidia 1660 ti or AMD RX570. Do CPU and GPU mining at the same time. Use CPU to mine Monero and with GPUs for example mine Ethereum.
Thats one of the things I am looking into, since I have 15 RX 580 8 GB.
The Ryzen9 3900x is a bit expensive where I live, but the TR 1920x or Ryzen5 3600 is cheap.
So thinking 3xRyzen5 3600 and B450 Tomahawk with 5 GPUs on each.