If this is your only lens, then try to get a good zoom lens. Any of the kit lenses will do. The ones that came with the D80/D90. Like the 18-70mm or 18-105mm.
My only advice would actually be the opposite -- never, ever buy a kit lens UNLESS you don't plan to shoot it normally. Kit lenses are "ok" but will start to really be a pain when you realize how high they're stopped up, or that their glass isn't nearly as flawless as you'd think.
I know nikon's kit lenses aren't as bad as canon's (in my opinion having used a variety of both), but the 18-105 suffers quite a bit of distortion if my memory serves me correctly.
Also, zoom lenses will cost more overall, and will not be as sharp as primes. Prime lenses tend (tend) to be a lower cost for a sharper lens with a lower f.stop. It's not always true, but it's often the case.
Personally, I recommend running with a Nikkor 50mm 1.4 as your only lens to start (if you're willing to pay for it), otherwise the Nikkor 50mm 1.8 is a better lens than canon's 50 1.8) since that's a very friendly focal length to start with for portraits and can be used to composite scenes as well. It's about a 75mm equivalent for your crop sensor (nikon is 1.5, not 1.6 I believe..? could be wrong.)
Last comment, I personally shoot with a Canon 50 1.4, and a Canon 135mm F/2 L-- aka. a very sharp and fast telephoto for indoor sports which I've shot in the past, as well as being an incredible portrait lens. The final purchase for what I see as a useful and "complete" range would be a 24 or 28mm lens, preferably at f/2 or 2.8.
Hope something here is useful to you
EDIT: I should also mention---- EVERY NIKON F MOUNT LENS WILL WORK. You can find lower cost older Nikkor lenses that are amazing, like a Nikkor 100mm F2 I picked up about a year ago for $20. Crazy sharp, crazy fast. No autofocus, but that's ok. People don't always realize the old Nikon lenses still have very high values. Most lenses will retain value generally, so when you pay out an arm and a leg, you can likely get nearly all of it back, if not all of it (assuming you don't buy retail)!
Lenses ho