Id agree with Sam, steer clear of the really cheap stuff, you will only end up buying again later down the line like i did if you go to cheap.
The Key thing is that what ever you get, is that your comfortable wearing it, as being un-comfy in the gear will drive you nuts.
Bare minimum stuff most would say is:
Helmet
Jacket (textile/leather)
Gloves (textile/leather)
Trousers (be it leathers/textile/kevlar jeans)
Boots (urban/touring/full)
Extra's:
Thermal neck tube / balaclava like dan said, is'nt a must, but is a nice extra, you can be as cosy as a bug in a rug, but if your necks open to the elements it can make a ride not so enjoyable.
If some of the stuff you decide on is'nt to weather proof, a 1 peice rain suit i would say is a good extra to consider, they just slip over what you normall wear.