Choosing a flight controller

[m_farooq (Muhammad Hamza)]

I am new to drones and want to make a simple RC drone with GPS capability that works efficiently. I want to know about some low-prized flight controllers with open-source software. Kindly help me select the controller.

[Mustafa_Gokce]

https://ardupilot.org/copter/docs/common-autopilots.html