I would take a look at Rhinoceros (MecSoft). Its very capable, easy to use, and you can get a student copy for 300-400 bucks.......I think. You can also download a free trial version that is fully functional with 25 saves.
Lynda.com has a very good set of video tutorials for using Rhino, and it costs about 25.00 per month you use it. It's a good start.