It all depends on what your ESC/motor combo is putting out. You didn't mention the rating of the motor.

Drift is not dependent on high revs. In fact, a high-revving system will actually hinder your drifting. You want something that is controllable, and tires play an integral part here, as well.

Speed is not the most important thing in drift. Control is. A system with a 4000Kv motor is a good start, but if you have something bigger, you can program it via your ESC, to something a little lower, so you can control wheelspin better. Give it a try, if your ESC can do it.

Also, have you seen the HPIdrift tutorial? It can be found at Youtube with a little searching (it used to be found fairly easily, but now you have to search a bit). That will get you going with the basics, and it's the easiest way to learn how to drift. Give it a shot.

If you want to getdifferent pinions/spurs, it's your decision, and it will add some gearing flexibility, but is not necessary if your ESC is programmable.

What tires are you using?