One of the most basic performance upgrades to a car is the suspension. Often OEM suspension can be a little soft designed more for comfort than performance. Some OEMS such as Audi & Nissan have now incorporated adjustable suspension that allows you to fine tune the suspension, but for the majority its typically less sophisticated.
Whilst upgrading springs alone is the cheapest way to achieve the lowered look, we'd recommend using coilovers vs just springs. When using lowered springs with OEM Shocks you are using less suspension travel than the was originally intended, this can lead to the shock failing or an uncomfortable ride.
For the serious track day/drifter - there are a multitude of other upgrades such as lower arms, traction control bars etc These all allow adjustment typically via rose joint mounts to perfect the handling of your car.