Hi, I'm new to this forum but long time Canon shooter.
The simplest suggestion would be the 50 f/1.8
http://www.bhphotovideo.com/c/produc...0mm_f_1_8.html
Maybe it is not wide enough for you tastes, the EF 35 f/2.0 isn't bad either but it is above your stated budget
http://www.bhphotovideo.com/c/produc...e_EF_35mm.html
In the same price range you'll find the EF 24 f/2.8
http://www.bhphotovideo.com/c/produc...e_EF_24mm.html
And the EF 85 f/1.8
http://www.bhphotovideo.com/c/produc...Autofocus.html
As you can see, starting from 50 mm it is a price/apperture trade-off. Except for the 24 I own these and really enjoy them. Taking build and image quality into consideration these lenses are not as good as the L glass I own, but the four of them together won't pay for a decent L lens.