There are so many factors to weigh here, that you're gonna have to give some more information. It also depends entirely on how much money you're willing to spend.
A good set of stock strut replacements (Bilstein, Tokico, KYB to name a few) and springs (Eibach, Intrax, Tanabe etc.) will run you around 600 + shipping. This also assumes you have access to a spring compressor, and your stock upper mounts are in good shape.
A set of coilovers starts at around 700 (Megan, Ksport) and go upwards of 1500 and higher (Tein, HKS, JIC etc.). The nice thing about coilovers is that they are adjustable. So, if you want to really dial in your ride height how you like it then this is the way you go. Also, dampening force can be configured much more with a coilover setup as anything out there now supports 16-30 'clicks'.
Some negatives to coilovers aside from the obvious price is that most if not all use linear spring rates. This is a *good* thing when racing/track/mad drifting Y0 as the response from your suspension is predictable. But, for a daily driver this isn't the most ideal from a comfort stand point. Non linear lowering springs like Eibach gradually increase in spring rate as you compress them. This is much more forgiving over bumps then your average linear spring.
In any case, you'll also want a set of quality sway bars. I installed a pair of performance techniques 2 weekends ago and the amount of body roll that these soaked up was amazing. I bought mine off of 935motorsports for $250 + shipping.
So think about what you are going to be using this car for the most and go from there. No sense going overboard on a set of coilovers when you hit up 1 or 2 events a summer and drive to/from work the other 99% of the time.