buffer - Drawing perfect circle with set radius in meters on map using QGIS?

Following this istructions on how to draw a circle I can make buffer layer on each point I need.

I am not able to draw perfects circle because the buffer will be elliptic?

The CSR is EPSG:4326 - WGS 84

And I am also not able to set unit misure in meters as I need (300 meters)

Where is my error? I use QGIS 1.8 on windowx 7