Unfortunately, that motherboard only has an AGP slot, so your videocard upgrade will be very limited.
Here is one of the cheaper units for AGP, but you must also ensure your case has adequate cooling (at least one case fan aside from the power supply fan is recommended) and also ensure you have a fairly beefy power supply (350 Watt or greater, 400W+ preferred). http://www.newegg.com/Product/Product.aspx?Item=N82E16814161318