rear bumper drags

The rear end of my car sits lower than my front end, because of this i've already screwed my rear bumper up that i just had put on. I need to know the cheapest way to raise the rear end of my car. I want airbags, but I just cant afford $1700 right now. I can spend around $500. I have a 99 civic.

New shocks and springs. Airbags are a COMPLETE waste of money unless you have a show car. Ride quality is neglegable and they DO NOT handle well at all handling performance wise.