For an electric helicopter you need:
Airframe
Motor
Speed Controller (ESC)
BEC or RX pack to power the servos
3 Cyclic Servos
1 Rudder Servo
Gyro (Flybarless Controller if going FBL)
Receiver, although quite a few FBL Controllers have the ability to act as the receiver if you plug the Spektrum remote satellite receivers into it.
There are many ways to setup a helicopter. Some Speed controllers have built in BECs and you don't need RX packs, some people prefer seperate RX units, some like to use FBL controllers with sats for cleaner looking installs with fewer parts bolted on.
All of the above will work great, there is no "perfect" way to do it.
My setup is:
Synergy E7 (although will work fine for E6)
Hacker A50-12L 470kv Motor
Castle ICE2 120A HV ESC
2s Lipo receiver battery
Mikado Full Size Vbar - Blue Line with 2 Spektrum DSMX Remote Sat Receivers (I don't run a seperate RX)
JR 8917 HV Cyclic Servos
Savox SB-2272SG HV Gyro Servo
I connect the receiver pack to the Vbar directly. The full size VBar has several extra ports for plugging in power.
I use one of these custom harnesses:
Deans plugs into the RX packs, and the two Servo leads plug into the Vbar like pictured here. The allan driver is pointing to the two servo leads coming from the battery:
The RX pack is strapped to the side of the frame, sorry I didn't think to take a picture of the pack, there are plenty of places to mount a battery.
I hope this helps.