Look up around pages on Alternate Cryptocurrencies, there are couple guides and one of them I bieleve from user tacotime he explains a lot there.

But it's basically something like this

Mobo: 80-120$ with bunch of PCI-E slots
CPU: 80-110$
RAM: 6-8gb
GPUs: 7950 should be found for 280-310$ as many as you can
Power Supply: Platinum or Gold on 1000-1200-1500 watts for around 150-250$