I struggled with this for quite a while.
You will need a separate power 3.3V power supply. The usb is not sufficient nor stable enough to power the ESP8266 while in operation. I would suggest you also use a 100uF capacitor or greater close to the power pins of the chip.
One other problem I encountered was not setting both the CH_PD and RST pins to high via a pull up resistor. It would not operate properly for me otherwise. Goodluck