Every card overclocking rating is difference.
Assuming that you're adjusting the power increase for an overclock I won't mention voltage.
Most basic graphics cards overclock is +100 clock and +200 memory.
You can overclock memory pretty easily up to 500-600 (max?)
and for clock speed +300 is on the high end (I wouldn't try adding 400 clock speed (could kill gpu)
if you want to be on the safe side
I'd run it at +200 clock
and +350 memory
at 115% power