It depends on how low you want your car. If the number of drop is below 2in, I think you can just go with lowering spring. If you are looking for more, go get coilover. If you are buying lowering springs, you need to research a little bit as different company has different drop numbers, and some companies even have different lowering springs (like Tein has S-tech and H-tech). The more you lower, the hasher the ride quality. And to a certain point of lowering, the strut/shock would not hold the load and you will just better off coilover.

If you are going coilover, you may as well get those pillow top mount. That gives you camber for the front. For the back, get the camber kit too. It is not like the car would handle like sh*t, but just your tire wear would just be too fast as inside of the tire would wear out faster than the outside.