Be aware that Gigabyte M/Bs can be a PITA to boot from a USB Stick.
I was unaware of this! Any known/suspected reason for this?
It is well documented, but if you dont know about it you can be running around in circles trying to figure out WTF is wrong. Seems to be something about DOS and FAT formats. There was a post by someone associated with the BAMT site about using two USB sticks as a work around. First stick loaded something, when that finished, the second stick loaded BAMT. The FAQ on BAMT shows compatible hardware and lists some Gigabyte boards as Not Compatible.
I never pursued it, I simply sold the two Gigabyte M/Bs that had caused me massive angst and bought two MSI M/Bs and that was the end of the problems with USB boot and getting PCIe slots recognised and working.
Only only the Gigabyte Company could tell you why they would set up something as Fxxcked Up as that.