Drifting.... here are some basics
Once bushings, ball joints and the basic matience is done
Project MU brakes shoes
Weir Diff kit
Steering rack spacers
Spare set of rims and all the tires you can get
SEAT TIME!!!
In my opinion you don't need all the fancy arms yet, you need to learn your car first.
Seat time is invaluable, if you can do it in this under powered boat of a car with no angle then you're golden
A lot of people spend thousands on suspension and then bomb at the track due to lack of seat time and cockiness
Start slow, do controlled donuts then move into controlled figure 8's once you've got that down you're ready for the track
After a track day or two you should be able to determine what you can do to improve, if suspension arms are needed then you drop $600 on them
Hopes this helps