hydro systems can only be sooo inexpensive...your going to have to buy nutrients. I think one of the cheapest ways would be to make your own DWC bucket. Requires a fish tank air pump...minimum of 3 gal buckets and some aquarium glue and lines and last but not least nutrients. Then you still gotta buy a ph meter and ppm meter. Im sure there is a DIY dwc bucket sticky around here somewhere.