rizzir, welcome to the forums.
Best place to start for that is the supported memory list of the board, GA-MA770-UD3 (rev. 1.0) - GIGABYTE
The list isn't the be all and end all for what works with the board as they don't have the time to test everything. It is a good place to start though. If it helps any just about any DDR2 should work, just a matter of how much you want to spend.