Start with any plastic storage create or dairy/milk crate you can get.
Get some modern gaming GPUs like these 270Xs. (Check PiMP Product pages for compatibility information, and Hashrates Sheet for expected hashrates)
Get a good, efficient, reliable PSU to power them all. Be careful choosing!
Install the PSU in the crate. Some people like to make piece out of whatever, or use Zip ties for the easy way.
Choose a motherboard, CPU, and RAM that will have enough PCI Express slots for your GPUs.
CPU and RAM is mostly up to you. The more, the merrier of course. CPU can be used for mining as well.
Install the CPU/RAM in the Motherboard and then install that in the crate. Install the cables for the SSD but don’t connect it just yet. (We need to put PIMP OS on it first.)
Install your GPUs. In this example, she made aluminum brackets to secure everything with a pro look and feel.
Now go write PIMP to the SSD, Plug it in, Hook up your cables and power it up.
You’ll be mining in no time.