On/Off Switch driving MOSFET from Battery
A few alteration to the circuit could be done. Somethings like this.
NOTE:

Putting n-channel MOSFET near to ground is recommended.
LED is a diode basically, whose voltage drop depends on the color(red:1.2V, green and blue: 3.3V), so a resistor in series has to be provided for LED not to get damaged.
If you are using 2-3mm LED(those small through hole LED), mostly you need 1-5mA of current based on brightness required. You can calculate something like this. Values of resistor should be calculated(They are for representation purpose only). R1 = (Vcc-Vled)/0.003




To limit the in-rush current on MOSFET Gate, we need a resistor R3.
To discharge the MOSFET Gate Cap, we need a R2