for me, I just use 1.25v as a starting point. Push the processor until it becomes unstable.

from that point, you can
a) lower the processor to a stable point on the same voltage
b) pump more voltage to maintain the speed

I usually go for a). After it reaches a stable speed, try lowering the voltage further. Once the processor is unstable, up it to the last stable voltage.

Usually people use Blend test.

For me i don't use Prime95. I just play games and do my work, if it's really unstable then games wouldn't get through.

Getting games through doesn't mean it'll pass Prime95 either. And not passing Prime95 doesn't mean it's totally unstable to use.