If you want to go REALLY cheap,just skimp on the pump for now.
77 Bonneville Heatercore-$15
Via Aqua 1300-$18
Swiftech Apogee-$40 with discount
Home Depot 1/2 Tubing=60cents a foot
There ya go,cheap yet performing wc system. You can check out the reviews of the Via Aqua,it gets good reviews. Do keep in mind though,there are several members here who have hands on experience,and they did leak.
Note:A non leaking still cheap substitute for the Via Aqua would be a Hydor L30. I was just trying to keep the price as low as possible.