If you need basic protection, consider iCarez. They sell an affordable 2-pack that gets the job done. Although it isn't made of glass like some of the others.
This company sells a 2-pack for only $6. It's easy to install, goes on clear, and works great. The glass screen protector from iCares has poor reviews, so we'll skip it for now. If you just want to prevent scratches, buy this.