Should buy a new camera or lens?

I'm thinking to buy a Nikon D800 or a 14-24mm lens, I've a D300s right now, but due to the budget I can only afford one of them…

Does anyone can give me a suggestion on which one I should buy?

The D800 is a fantastic camera. If you have lenses for it then get the camera. Later on you can buy better lenses.

Lens last forever. But if you see something that d800 has in improving your image quality, that its worth going camera rather than lens.
i'm thinking on upgrading because new camera has higher than 1600 iso, new camera will give me flexibility of max 25600 iso

Having a Nikon D300 myself, I understand your dilemma. But be forewarned that you probably have a camerabag or two filled with DX lenses, which you'll need to replace in order to fully appreciate the D800's FX full-sized sensor. All your Nikon DX optics will automatically switch your FX Nikon to DX mode.

If you are still thinking of going FX, might I suggest the new Nikon D600? It's gotten some pretty excellent reviews and is a reasonably priced entry into the FX world.
http://www.dpreview.com/...nikon-d600
http://www.kenrockwell.com/...n/d600.htm
http://kenrockwell.com/...0.htm#comp

Me? I'd get the lens. I'll replace the body when it dies.