[cdgatti]

all depends where you are starting from:

If you are completely stock, something like this order would be recommended:

1. Improved dampers, like Koni or Bilstein (with an e92, assuming rwd, this would be Koni Yellow or Bilstein B8.)
2. If you want to drop it lower than stock sport, then BMW performance springs or H&R/Eibach springs or you start down the higher dollar path and go with coilovers. That is another world altogether and you will have to start researching. Popular options are Bilstein, Ohlins, KW.
3. Then M3 control arms for the front and remove the strut pin to max negative camber.
4. Then M3 arms and subframe bushings for the rear. Can also do Dinan or Monroe top rsb to remove some bounce.
5. Then front sway bar, an e93 M3 bar is recommended. This is the stiffest oem bar. There are also aftermarket bars.
6. Then a LSD for your differential.
7. Then a M3 rear sway bar.