I'd like to play devil's advocate here and say that while I have been in the camp of not using flash in broad daylight, I recently obtained a nice SB-600, and I must say the number of keepers, and kind of shots I can take have vastly increased. Not only does it fill in the shadows, it adds a night catchlight to eyes, and somehow allows me to shoot at low iso. Apart from that, backlit shots no longer need major exposure compensation. And allows me more kind of shots that I can take.
Here's a few:
D200, 70-300VR, SB-600 set to balanced fill. Iso 100. In the shade....
D200, 70-300VR, SB-600 balanced fill.
Totally backlit shot; usually I will +ev, and lose the background. This time, using balanced fill, I can keep the background properly exposed, and yet fill in the foreground with flash. In this case, the flash could have been -ev'd a little bit, but this was a very early shot using the sb600.
D200, 70-300VR, Sb-600 balanced fill.
Adding in a very nice catchlight, and filling in the shadows.
D200, 16-85, Sb-600 with balanced fill.
In response to the OP's question though, I'd suggest getting a lens first (with a focal range complimenting your currently lens) to figure out what kind of focal range you are most comfortable with for the kind of stuff you like to shoot.I have a 18-55mm vr lens.
I been wondering whether to get a zoom lens that can enable me to zoom further to take animals. However i also want to take night shot too.
Any cheap lens to recommend for zoom lens?
Night shots? Static objects = tripod. Else... a fast prime perhaps? The upcoming 35/1.8 afs looks sweet and affordable.
If you want to zoom futher with your current camera for "cheap", I'd recommend the 55-200VR. It's good, highly affordable, used to have it till I saved enough for the 70-300VR.