For the CP2 I would recommend you get the following parts.

Main head - get at least two of them
Blade grips - an extra set should do it.
Flybar seesaw - get a few of them. Ive broken countless numbers of these.

What normally happens with the CP2 is that you break a ball link off of one of the above parts rendering it useless.

Of course blades, tail motors, flybar, skids and canopies are other parts you may need.