Dedicating more RAM to graphics from within the BIOS or via registry hack will not improve graphics performance. The only time that you really need to increase this amount is if you have a buggy game that insists on having a certain amount of dedicated RAM before it will start (if this is your situation, don't forget to report this bug to the gamer developers!).
It is unclear whether overclocking will improve the frame rate; it simply depends upon way too many factors. You can try if you wish, but remember that you can void your warranty doing so.