Here's what I put together.
Get this motherboard bundle at Microcenter (they knock $30 off CPU/MB bundles for in-store purchases):
http://www.microcenter.com/product/5000235/AMD_Ryzen_5_1600X,_ASUS_Prime_B350M-E_CPU-Motherboard_BundleGet the rest of the stuff here:
https://pcpartpicker.com/list/NkpHvVThere are mail-in rebates on a couple of the items, but after rebate, should come in under $800.
If you want a optical drive, you can add any cheap one you want. If you need a copy of Windows, you can get inexpensive product keys on /r/microsoftsoftwareswap. Just download the USB installation media from Microsoft.
If anyone else wants to tweak this, go ahead (I haven't put together a build in a little while...and holy fuck, have RAM prices gone up).