Unfortunately, you didn't say which camera you're using. What's "wide angle"on a full-frame camera could be "standard" on a 1.6x FOVCF body. Here are some examples:
  • 20mm on 1.6x = 32mm on FF
  • 24mm on 1.6x = 38mm on FF
  • 28mm on 1.6x = 45mm on FF
  • 30mm on 1.6x = 48mm on FF
  • 35mm on 1.6x = 56mm on FF
  • 50mm on 1.6x = 80mm on FF
  • 85mm on 1.6x = 136mm on FF



It will also depend upon how far you are from your subject. If you're in a room in a house, that's very different from outside at a playground. Studios are usually somewhere between. In the "old days" (35mm film!), we called an 85-100mm lens a "portrait lens," because it was useful for head & shoulder shots that looked natural, at least to Americans. (People who grew up elsewhere might be more used to a closer perspective, for example.) For full-body shots, we used 35mm, a person is a bit more than twice as tall as her head & shoulders--ergo, you have to use a bit less than half the focal length. We called a 50mm lens "standard" as it produced an image that looked pretty much as it would to us with our eyes and brains. (Remember that perspective doesn't depend upon the lens but merely upon the relative position of the camera, subject, and background.)


So, if you're using a 1.6x camera, a 30mm lens would be "standard," 50mm would be "portrait," and 20mm would be "wide."


Is there a reason for using primes? Do you need the extra speed/wider aperture? Don't be fooled by the myth that "primes are better quality" than zooms. The best primes may be, but many are not. The 24-70mm f/2.8L is higher quality than many Canon primes in the same focal length range, for example, unless you go to the very expensive L primes, which cost more than the zoom. If you don't need the wider aperture, the 17-40mm f/4L zoom is $765 new, less used.


Having said that, here are a few primes that aren't too expensive
  • Canon 20mm f/2.8 USM ($500)
  • Canon 24mm f/2.8 ($325) old design, but can do a nice job for the price--a lot less than the 24mm f/1.4L II! I recently replaced this.
  • Sigma 24mm f/1.8 EX DG DF ($479)
  • Canon 28mm f/1.8 ($500)
  • Sigma 30mm f/1.4 EX DC HSM ($439) I have this lens--it is very nice!
  • Canon 35mm f/2 ($320) old design, not USM, but it still works, and is quite cheap. I also have this one.



Once you figure out what focal length(s) you need, you can make your choice.


Another word about wide apertures: They can be less-than-useful when photographing people if you're close, as the person's entire face/body may not be in focus. Here are some examples, computed with DOFMaster:


35mm @ f/1.4, 6 ft: 5.77-6.25 ft, that's about 3 inches in front and behind the focal distance.


50mm @ f1/4, 6 ft: 5.89-6.12 ft, or about 1.5 inches each way! If the person's eyes are in focus, her ears and tip of her nose may not be.


Use a shorter focal length:


28mm @ f/1.4, 6 ft: 5.65-6.39 ft


or narrower aperture:


35mm @ f/2.8, 6 ft: 5.56-6.51 ft


50mm @ f/2.8, 6 ft: 5.78-6.24 ft


or back off:


35mm @ f/1.4, 10 ft: 9.38-10.7 ft


50mm @ f/1.4, 10 ft: 9.69-10.3 ft


etc.


When you're considering "full body" shots, remember that the subject's face and feet are at different distances from the camera. Focus on the eyes and the lower torso may go out of focus. You have to experiment to see what works for you.