I'm always more for a "traditional" designed flash. Starting out, make sure it has i-TTL and CLS compatible. One of the reason to get Nikon is for the flash controol built in. A SB-700 would be ideal but that seems to be out of your price range. Yongnuo has some good options. I have a post above in the thread with some really cheap options that should be available in your area (at least 1 of them.)
One thing to keep in mind is that you DO get what you pay for with flashes. The cheaper they are, the worse performing they are. Color shifts, bulbs going out, much lower power, lack CLS or even basic TTL.
As for the trigger: Your pop-up flash should be able to control the off-camera flashes. You can turn off the pop-up and still control the off-camera flashes. It is a bit unreliable in bright sunlight situations, but it does the trick in many cases.
Comments
Thanks for your comments
A nikon 910 bit expensive looking to spend up to £100
Any ideas?
Buy from a UK source or you may get customs duty ..try http://www.ebay.co.uk/itm/Meike-MK300-MK-300-LCD-TTL-Flash-Speedlite-For-Nikon-D3000-D3100-D3200-D5000-D90-/301069732609?pt=UK_CamerasPhoto_CameraAccessories_CameraFlashUnits_JN&hash=item4619278b01#ht_7465wt_1190
do not buy the Jessops 360 thing or the sunpak 2000 equivalent of the SB400 both horrible
If you want off camera the only way to go is the YN 622N at about £25 each ..you need two and dont need the latest YN622 TX N
One thing to keep in mind is that you DO get what you pay for with flashes. The cheaper they are, the worse performing they are. Color shifts, bulbs going out, much lower power, lack CLS or even basic TTL.