You will need three servos for cyclic, 1 servo for rudder, 1 servo for throttle.
You will need a FlyBarless controller of your choice.
You will need a sensor for RPM.
You will need a motor of your choice.
You will need a battery pack to power the electronics.
You will need blades, main and tail.
You will need some fuel accessories, pump,
Tubing, filter for fuel tank, filter for fuel line on the Heli,
Probably a “T” fitting for ease of fueling and a fuel line
Shut-off device. I actually run two, one on each side of the T fitting.
This is a pretty comprehensive list of extra stuff needed.
I hope I didn’t overwhelm you. I don’t think I missed anything that you will need.