The cheapest and effective hydro system is a DWC setup. You take a 4-5 gallon bucket, add water, an airstone, a $7 fishtank airpump, and nutes.

The whole project literally could cost you nothing if you have that stuff lying around. A trip to walmart for everything needed would cost less then $16 or so a bucket. (Or you could use those 10-15 gallon rubber maid tubs)