50mm f/1.8 II, often called the "nifty fifty" by pros. It is the best value for money lens out there. 50mm is the normal focal length, so no distortion (as opposed to if you use a wide angle lens to shoot a large group photo). It is very inexpensive < $85 today, (mind you, I bought mine 2 1/2 years ago when it was selling for $65 on Amazon, so interestingly, same lens, but it has gotten more expensive). With an f stop of 1.8 (hence a fast lens), and if you use a tripod, you have all the tools you need to get very natural photos in available light. You could spend a whole lot more on fancier lens, but this will do the job for a fraction of the price. I have many other better lens, but this is the one I will always have in my bag, because it is very light, no problem with handheld, it will perform admirably where other lens can't (e.g. in low light).