The Silvia (S13, S14, S15) can drift with NO tune and NO parts. It's all in the technique.
Even then, there's no magic amount of engine upgrades or suspension configurations that will make the car 'drift', it already drifts. The tune can make it easier or teach/show you how to drift better, but the car can drift without anything extra.
The tune UrieHusky linked says to buy all of the upgrades, including engine ones. I do not think it is necessary if you can improve your driving without them, though.
That would be just boring to drift it stock. I want to build a drift car but NOT a car which drifts only by steering a little . I want to do the work on drifting.
Why don't you do what every other single person in the drift forum has managed to do and click the stickied link at the top of the page that clearly has the words 'Drift' and 'Settings' in the title.