If you are planning to build your first quadcopter but are not too sure what parts you need to buy Sam wrote a quick guide on some suggested parts for building a quadcopter over on dronetrest.com.
The kit is based on the popular F450 quadcopter frame as its cheap to buy and very easy to build. The idea behind this kit is to include parts that are easy to use and not too expensive to replace should you break something as you are learning to fly. The suggested flight controller is the CC3D which is also quite easy to setup and use. Once thing to bear in mind is that this CC3D flight controller does not include a GPS module out of the box so you will only be able to use this controller for stabilisation and not for full 3D waypoint flight unless you add a GPS module. However both the motors, frame and flight controller are good enough that you can easily add extra things and features such as FPV, or GPS to you can fly a more advanced quadcopter. If you need some more details on all the parts you need for a quadcopter then I suggest you also have a look at the parts list for arducopter to get a better idea of all the things you need to build a quadcopter.