As Pranav stated, get the 50mm prime lens. This is a must have lens for beginners, and is fantastic for portraits because of the focal length on an APS-C sensor, as well as the shallow DOF at f1.8.
Hmm generally the all in one walk around lens compromise on IQ. Hence I suggest if you can save get a Tamron 17-50 f2.8 non VC for 18k its as sharp as the 17-40L lens plus has a fixed fstop at 2.8
Cranky: What you say is correct, but the recent lens with Image stabilization are of a huge boon here. The Canon 55-250 IS is one of the best VFM lens at 10.5k, and in good light you can take good snaps without tripod at 250mm. The thumb rule is shutter speed should be 1/focal length, hence for a non IS lens you will need to click atleast at 1/250 of a sec to get a jerk free shot, with IS on you can take the same shot at 1/100