If you can afford the 17-55mm IS f2.8 it's better than primes (imo) for a fast-moving production. f2.8 is fast and allows for relatively shallow focus*, you can zoom without the aperture changing, and the image stabilization is invaluable. But the lens is over $1,000.
For my money, if you want a versatile kit with EF mounts, the 17-50mm IS f2.8 tamron and an 85mm f1.8 Canon is the best choice. A set of primes covering these focal lengths (16mm, 24mm, 35mm, 50mm, 85mm or something) would be faster, but with no IS. A long lens can also be nice. I use the 55-250mm IS when I need a long lens outdoors, but its utility is limited. The 50mm f1.8 is a fine lens optically, it's just that pulling focus is extraordinarily hard with it. The more you'll shoot the more you'll know what lenses you need.
Also, don't skimp on a good tripod. You'll want a decent fluid head (501 or better) or else you'll get ugly jumpy footage. I just did some shooting with a 7d and t2i and stabilizing these cameras (either with IS or a steadicam/tripod or both is crucial).
*In "Hollywood films" f2-f2.8 are the normal f-stops for night exteriors, f2.8-f4 for night interiors, f4-f5.6 for day interiors, f4-f8 for day exteriors, etc. in general. Some deep focus films shoot deeper stops and extreme low light lenses allow for t1.3 (f1.2), which is used occasionally for night exteriors, but f2.8 is often as fast as you need; beyond that shallow focus can look "cheap" like you can't afford more lights.
