Marciokoko:
originally I wanted to build one (like everyone does) with an L293D and 4 brushless hubsan motors i bought online and was quickly alerted to the fact that those motors draw quite a bit of power and i needed ESCs and a flight controller.
The L293D is not a Brushless DC (BLDC) motor driver. You can use it with brushed DC motors as used on many micro-multicopters and nano-multicopters but not the more efficient BLDC motors used on larger multicopters. Since you generally don't need to run the motors in reverse, a simple MOSFET is all you need for brushed DC motors. The ESC's (Electronic Speed Controls) drive BLDC motors.
You can use an Arduino as a flight controller. The main purpose of the Flight Controller is to translate the Throttle, Elevator, Aileron, and Rudder signals from the RC receiver into power level signals for the four motors. Adding an accelerometer and gyroscope allows the Flight Controller to stabilize the multicopter, making it easier to fly.