You don't necessarily need to spend the money for the L series. I'd rather have a selection of primes to work with, to have choices for use in different situations.
Personally for this sort of thing I usually use Canon 20/2.8, 28/1.8, 50/1.8 and 85/1.8 on my crop cameras. (I also use 135/2, but mostly on full frame.) These are all USM lenses, Canon's "mid grade" build quality. Still reasonably compact and not too heavy, so it's not a big deal to carry four of them around in my camera bag.
Depends upon what you want... how much you want to drop out the background, how much workng space you have. Longer lenses can blur things down more, as can larger apertures. Conversely, with wider lenses you have to be careful not to work too close when photographing people, a wide lens will give perspective and anamorphic distortions. Can't be helped, it's just the nature of optics, working distance, and wide angles to do so.
Yes, the Sigma 30, 50 & 85mm are all also quite good, too. They all are significantly larger and heavier than their closest Canon equivalents. The 85mm is f1.4, so 2/3 stop faster than the Canon 85/1.8, but is also more expensive. The 30mm is "crop only", while all the other lenses I've mentioined are usable on both full frame and crop. These Siggy lenses all have HSM, which is Sigma's version of USM.
If your budget is tight, the Canon 50/1.8 is a great deal for occasional use. And Canon 28/2.8 or 24/2.8 might serve as a wider budget lens. None of these lenses have USM, so AF will be a little slower, noisier and perhaps a little less consistently accurate. They are capable of good image quality though... The IQ differences between them and the more expensive mid-grade lenses (or even comparable L series) will be fairly subtle. For example, the 50/1.8 vs the 50/1.4 at almost 3X the cost, the mid-grade lens has better AF and build quality as noted.... IQ with the "better" lens will be seen as slightly more saturated colors and better contrast, a little more resistance to flare, somewhat nicer backgrond blur (due to more leaves in the aperture, to form a more nearly round opening).
Premium lenses such as 24/1.4L, 35/1.4L 50/1.2L and 85/1.2L take a step farther allowing for greater control over depth of field, plus really lovely background blurs, though they can be slower focusing (the 50mm and 85mm put the emphasis is on accuracy rather than speed, due to the shallow DOF potential) and are roughly 3X the cost of the mid-grade lenses, 8X or 9X the cost of an entry-level model. They are also a lot bigger and heavier.