In reply to RBonney: I've got a D7000, which has optical triggering inbuilt - great for quick shots but isn't that reliable when the angle starts getting weird. For serious (or paid) work, I use a set of Phottix Stratos triggers - about £100 for transmitter and 2 receivers - which allow multi-channel work*. All you need to go with them are cheap third-party manual flashguns (they aren't TTL triggers, so no need to pay for TTL flashes). If you want remote TTL, you need either Pocketwizards, Phottix Odins or a Nikon SU400 (and Nikon flashes); any of which will be expensive!
*you could probably use cheap ebay ones instead, but using triggers of some sort will be the only way to get multi-channel remotes, let alone TTL, with the D3200; using a "dumb" optical signal alone will fire every flash that can see it at the power it is set to. The reason I like multichannel is that you can test-fire each channel separately, easily flick between two setups etc.