1. How much your money provide to build a Rig?
2. How many GPU will you use mining?
I assume you don't have a problem with providing your money. you can choose these
1.Motherboards:
-Asrock H110 Pro BTC+ (13 GPU)
-Asus Prime Z270-A (default 7 GPU)
-Asus Rog STRIX Z270E Gaming (default 7 GPU)
-Asrock H81 PRO BTC R2.0 LGA 1150 (6 GPU).
2. Processor enough Celeron if Intel Chipset.
3. RAM 4 GB or more 4GB better.
4. SSD 120 GB or more, choose Samsung.
5. PSU adjust how many GPUs. get PSU has 80+ such EVGA, Corsair.
6. USB Riser
7. GPU AMD cards (RX 580 8 GB, Vega). NVIDIA cards (1070,1070ti,1080ti).
sorry dude, maybe I can't give in detail how to build RIG from zero to hero. you must OP specific problem.