Firstly, I can understand why you've bought various spare parts, but stop buying kit.
1) Take the motherboard (Either one) - put it on a cardboard box, seat the CPU, insuring it's in correctly.
2) Take a known working PSU (If it's a Corsair one, do the paperclip test - Google it) and install just the 24v rail and the 8 pin aux connector
3) Install the RAM (It's deffo DDR3, right? You haven't ordered DDR4 by accident?)
4) Install a cooler on the CPU and wire it up (I.e. fan)
Turn it on. What happens?
If you reckon you've gone through two boards, two CPU's and 2 sets of RAM, it's either EXTREMLEY bad luck or you're doing something wrong.