best website for discount parts ? i have some but they don't seem the best

like getting ddr4 16 gb 2*8 for like 30$
or a really cheap good mid tower case for atx
Pretty much discount anything...

pcpartpicker.com compares a few major sites. Amazon and Newegg have sales all the time, but not super great sales. Newegg has shell shockers that can go up to 70% off of something. As for used parts, our classifieds here on OCF are a good place to start, Can usually get great deals on used hardware of varying wear, just have to do some digging.

pcpartpicker and slickdeals.net