I would suggest AMD cards over Nvidia just based on hash verses price. Here is a link that might help you with an informed decision.
The rest is my opinion and how (with the help of a friend) my rig is built.
128gb SSD HD
4gb ram ( I have 8gb since run a VB for Linux for Zwallet)
you truly only need a 2 core processor - if you go more its because you wanted to spend more $$$$
O/S either Win10 64b or Linux (you currently need Linux if you want a zwallet)
Mobo - depends on how many cards you want to run, if 4, then will work as long as they have as many pci slots has cards. Now 6 or 7 or 8 cards then you want something high end like the z97 or equivalent.
PSU, find the card you want, then how many you are going to run, then find the watts needed to run each card then multiply that by 1.75 then add 225 for mobo, HD and risers, fans.
The x1.75 is so that you find the sweet spot in your PSU and to avoid spikes and over heating. There are tons of posting about the PSU sweet spots, and if it matters. Again my opinion it does matter.
hope it helps, good luck