Portrait Lighting - Need Suggestion?

I'm a wedding photographer but strangely I never use any umbrella or soft box lights. I just use SB-700 with card bounce. But now I want to practice portraiture with soft box lights. Can you please guide me that which soft box should I use to initiate my practice? Please also give me the link to amazon.ca to buy those lights.
Gear: Nikon D800, Nikkor 24-70mm and 50mm 1.8, SB-700

Http://www.amazon.ca/s/

You have the right lens, the 24-70 mm f/2.8, but the prime lens you need for shooting portraits is really the 85 mm lens

For shooting portraits, you need at least a key and fill light as well as a back light and background light.

This means that you need to reconsider your lighting choices.

* you can use an incandescent lighting kit… The least expensive option
* you can buy some studio electronic flash units like Alien Bees
* you can buy more Nikon SB700's and control them from your camera.

You can use different light modifiers to shape the lighting in all three choices

You can do fine portraits with the lenses you have.

This sort of softbox
http://www.amazon.ca/...005HEGS46/

is designed for use with speedlights & will be ideal.

I have one identical & this is the result I get;

there's a SB600 used in that softbox & it's triggered using Nikon CLS (although I also mostly use radio triggers, RF602's).

You can add further lights/modifiers to your kit as funds become available, but it's perfectly ok to start off with a 'one light' setup for now. Those lights can either be more Nikon speedlights, or cheaper manual flashes (I use a mixture of YN560's and Nikon speedlights).