|Sorry about the missing link. It is now here.|
The Gigabyte board has a neewer chipset that supports higher memory speeds. However, it only supports 2 RAM modules so upgrading to more RAM means discarding the existing. For a budget build 8GB is enough though.
I suspect you have 2 different issues going on here.
Without rereading this entire thread I will point out some things that can go wrong.
Connecting the monitor to the wrong port or using adapters in the cable.
Failing to connect all wiring, which includes the 24 pin power, the aux. power, any required power connectors for your graphics card.
Installing the CPU without thermal pad or paste. The APU probably came with a thermal pad. After removal, you MUST clean off ALL the residue from both surfaces and then apply new pad or paste. Paste should be applied to the center of the APU applying an amount equal to a pea.
Failure to connect the CPU(APU) fan to the correct header.
Starting the board with the clear CMOS jumper in the clear position. This may damage the board. It has been known to come in the clear position. For a 3 pin header the run position should be pins 1&2.
I suggest you clear the CMOS using the jumper while the board is not powered. Temporarily move the jumper from 1&2 to 2&3 then back to 1&2.
IF the BIOS version is the problem you will NOT be able to update it without video. I am not saying the BIOS version IS the issue, just mentioning it might be.
To bench test the board all you need connected are the following. 24 pin & aux. power. APU, monitor to VGA would be best. 1 stick of RAM, keyboard. NO case to board wiring and no drives. No peripheral hardware either.
You start the board by momentarily shorting the 2 power pins with a screw driver. Pull the plug to stop.
If this test is successful you should see the board POST with a message indicating there is no bootable device.
If this fails then there are only three possible items to blame. PSU, APU, motherboard. BTW, did you receive a miniature speaker the connects directly to the motherboard? If so, you will need to connect that so you can hear the single beep indicating RAM present.
Try the above and get back to us.