I'm in doubt of things here.

Can 555 be used to supply gate signal to the Mosfet ? Is that recommended ?

The signals generated by 555 is square wave so does that makes it a PWM signal ? Or something are needed to be added with 555 to make a complete PWM circuit ?

 

The output of a standard NE555 or NE556 can can source or sink up to 200mA, and works between 4.5v and 15v, sufficient to supply many output transducers directly, including LEDs (with a resistor in series), low current lamps, piezo transducers, loudspeakers (with a capacitor in series), relay coils (with diode protection) and some motors (with diode protection).

The low power version ICM7555 can sink or source up to 20mA.

As for PWM, see http://www.instructables.com/id/Very-simple-PWM-with-555Modulate-every-thing/

 

Yes, a 555 or CMOS 555 can drive a nMOSFET quite nicely. A pMOSFET is slightly more problematic, as a conventional 555 can only get to 1.2V of the Vcc, but most cases it is OK too.