Connect the Pi to the GPS sensor and the FPV transmitter.

Depending on the voltage level, the GPS sensor might need to be connected directly to the Pi without TTL converter. 

Connect the Pi to the Camera module.

FPV transmitter and the Pi might be powered from the ESCs or from the drone power distribution board (depends on the voltage)

First, you need to enable the Pi Camera and disable using Pi Serial interface via this command:

sudo raspi-config

 Then, install the GPSD package and its Python bindings:

sudo apt-get update
sudo apt-get install gpsd gpsd-clients python-gps

 After GPSD is installed, I recommend disabling its automatic start:

sudo systemctl stop gpsd.socket
sudo systemctl disable gpsd.socket

Now, if your GPS sensor is hooked up to the Pi's serial interface and is designed to run at 38400 Baud, run this command:

stty -F /dev/ttyAMA0 ispeed 38400

If you are on Pi Zero W or Pi 3, you might need to switch up the default port:

stty -F /dev/ttyS0 ispeed 38400

Finally, start up the GPSD service manually (use /dev/ttyS0 port on Pi Zero W or Pi 3):

sudo gpsd /dev/ttyAMA0 -F /var/run/gpsd.sock

You can now try out if your GPS sensor works ok by launching CGPS:

cgps -s

If this command works fine, you should be able to use Python to get the data from the GPS sensor!