The kit from AIR BAG IT uses bags front and rear.
An air bag is like a tire the only time you need a compressor is when you increase the pressure in the bag.
If your intent is to set the ride height and not change it the you could get by without a compressor, tank, controller.
It all depends on what you want to do with it. The larger the components,compressor, tank, lines, valves, the faster you can raise or lower the car.