Hi guys, just would appreciate some input . I already have the Nikon 700 flash ,but debating on whether I should get another one or a small studio kit ?
I'd vote for a small studio kit with a lightbox, and umbrella and a background light. You can always use your SB-700 to help, but you'll be more at ease doing portrait with a larger flash.
You may consider honing your skills as a portrait photographer using natural light first before you throw down a lot of money on lighting. Natural light is a heck of a lot cheaper and combined with reflectors you can do pretty much do all the same shots, if not more. However, you may run into a little trouble if you're doing a lot of nudes.