Lenses, lenses lenses. So much choice yet not all are created equal. We've all seen professional photographer rock a huge 200mm lens and appear all important in a 400sq room. Well, maybe not all of us but if you get to know your gear you'll end up with better choices and effective results.
Now that being said if i was on a super tight budget and only had one choice of lens in my arsenal of gear it would totally be a 24-70mm 2.8 L mark II for a cheap 2000$. BUT the world can't always give us what we want right away so my best alternative is the oh so sweet 50mm 1.8 or 1.4 from Canon.
It's just a great all around multi purpose lens that can give a little to any branch of photography your diving into. I've used it in event with very low light and i have to say that the results are fantastic. But there is some learning and adjusting as you get to know the lens a little better. I really like the portrait style it gives off when photographing people and it's also doesn't require you to get to close like a 28mm where your practically in your subject's bubble.