Don't know what your budget is, but if you like the Canon 20D EOS Digital SLR for instance for your future camera, you could get an EOS lens that fits both your Canon EOS SLR film camera for the course, and the 20D.
Budget wise, a 50mm prime lens is cheap but not going to serve you well shooting content unless you have a big studio. If the money is there, invest in an L series lens. And do research ->
www.dpreview.com the reviews are outstanding.
