Mosfet's Vgs and rds
That i have to switch 50 positive supply, so i have to give more than
  50v for the gate to turn it on.


The absolute value of gate voltage is irrelevant - it is the difference in voltage between gate and source that will cause a MOSFET problems. With a high side N channel MOSFET with 50 volts on the drain and (say) 60 volts on the gate, the source will be pretty hard-connected to the drain and it will be at 50 volts (minus a small volt drop due to Rds(on).

But you have to be careful; when you activate the gate from a 0 volt level to 60 volts, you have to do so in such a way so as not to leave the "source" voltage behind should it be connected to a high capacitance load. In other words you MUST place a 15 volt (for instance) zener diode between gate and source to clamp the gate drive voltage to no-more than 15 volts. You also have to consider the scenario when turning off the MOSFET - capacitance at the source could keep the source at a high voltage (50 volts) and if you whip the gate down to 0 volts then you get more than -20 volts between gate and source.

So back to back zener diodes are needed OR use a proper gate driver IC.