Well, i mean, 500$ is for the gun. Used it may comes with some mags and a battery, a least. So no worry for that.
For gear (boots, vest and etc) and accessories (scope, laser, bipod or whatever), its something else. Its gonna be buy later, progressively. But for strating, 500$ for a gun (in used). I dont reallyplan to buy new now. Just get used, so it may come with approximatively everything i need for starting with a gun. You know what i mean ?