Best Lens Under $500 for Canon Mount

Hello

I'm switching over from my XA10 to a DSLR camera. This camera will be used for film only. I'm beginning production on a short that I am more confident in than I ever have been and I want to make sure I get the camera part right. I'm looking to buy one lens for under $500. I would be okay with something used I just want the best I can get on that budget. I really like the shallow depth of field look and want to be able to get a little of that even in a wider shot. If anyone can sudgest a lense I wiuld be very grateful.

Thanks

Michael