if you have to ask, you shouldnt do anything with drifting
Wrong attitude towards someone that is trying to learn about drifting. I bet you didn't know everything when you first started.
First thing is first. When you start building a drift car (or anything related to motorsports), you need to remember that money makes the world go 'round. Suspension for example, you can buy a $600 set of Nex coilovers on ebay and have the shocks blow within a month, or spend the extra few hundred bucks on a set of Stance coilovers and be happy with them.
Again, the first major modifications would be suspension and a differential. Don't worry about a sweet turbo setup or how much hp you need to drift.
Since you are first starting out, a set of coilovers and a VLSD. If you can afford to get a clutch type LSD such as a 1.5 or 2 way, I would very much rather get one of those. The VLSD would work just fine, though. A welded open diff is another choice, but I would rather get a true LSD since welded diffs usually break and are just not good for traction.
Tires are another thing that a lot of beginners overlook. Look, we are not pros and most of us are not sponsored. So don't worry about getting a set of Falken Azenis RT-615 or Advan Neova AD08 (as if your stock ass motor can spin them anyway). Sure, up front you want something that wont have you plowing the nose of the car into the wall, so spend your money on good front tires, but in the rear, it's cool to be a little cheap, because you are gonna kill the tires anyway. Used tires are good too, but you never know how long they will last.
Once you have master a car with a setp like this, it'll be time to start looking at other aspects of the car (power, grip, weight, and etc.).
