I have a nikon d3100 what would be the next lens to buy?

I have a 18-55 and 50 1.4G. I'm into taking portraits and was wondering what the next best lens to buy would be? I'm wanting to do this seriously eventually so i need to make a very smart decision on my lens.

These lens take pretty good portraits: Nikon 85mm af-s 1.8g or 1.4(if you can afford it). Nikon 70-300mm af-s, Nikon 70-200 af-s 2.8g. All those lens I mentioned creates beautiful smooth creamy bokeh.

If you have not already done so, the next thing to buy is a good tripod. A macro or a telephoto lens could be good to have, but you need a good tripod to make best use of them.

Your 18-55 and 50 are all you need for now. Consider buying a tripod and/or a nice flash.

For portraits, the 85mm f1.4G. My go-to portrait lens is the a-mount equivalent of this lens - Carl Zeiss 85mm f1.4.It's a perfect focal length and the wide aperture is great for blurring the background. If you can't afford the f1.4, the 85mm f1.8G is almost as good.

When doing portraits using either your 18-55mm or your 50mm f/1.4, what are your complaints? If you find yourself too close to your subject, get a longer focal length lens like an ~80mm. If you want to get closer, get a 35mm. If you want to blur backgrounds more easily than your f/1.4 lens, get an f/1.2, f/1.0 or f/0.7.

http://keerok-photography.blogspot.com/2011/05/lenses-so-many-of-them-there-is-no-best.html

My advice? Buy lens later. Seriously! Learn more on photography first.

Portraiture is all about lighting. You will have to buy both a lens and adequate lights into your budget.

In fact, you may want to consider upgrading your Nikon camera to one that will be capable of remote controlling Nikon speedlights (Nikon CLS system) or buy a SU-800 for about $250 that will remote control the speedlights too.

The classic portraiture lighting setup is 3 flashes - although you can use a reflector to substitute for one of the flashes. Typically you will have a Key (main light), Fill light, and a rear highlight. This is typical for studio use, but you can possibly get by with one flash for on-location.

At any rate, the built-in flash on your camera is not going to cut it for portraiture.