dont buy a rtr drifter. half of fun and understanding is in the building of the car. then you will also understand how it all works and when and how to modify it.
the chassis does make you a better drifter, but only by 5%+-. practice practice practice, if you start with something like a sprint2 or a tamiya tt01, then after a few months upgrade once you know the over and understeer characteristics of the car and how to handle it when you get in trouble.

one of my crew just bought my TA03 after using a tt01 for 3-4 months and practicing his butt of with it, now with the understanding/knowledge of how to drift etc. the upgraded chassis has made him better and he is now faster than before.

on the subject of tires.
HPI drift radials are awesome, if you run a stronger motor. like a p2k2, 19turn,17turn and lower or maby brushless.

ABS or PE (poly ethyline (the best))
very slippery and can create massive drifts whilst having total control. one of the best combo's of grip and drift.