I would recommend
Paper
Extra Smooth 250 gsm Bristol Board Pads - WINSOR & NEWTON
This is the smoothest paper and as such the recommended surface for portrait work. Its really thick as well!
Would also recommend some Cartridge paper for your rough prep sketches
Pencils
Any Derwent set should do the job nicely. You will land up using some more than others, which is great as you can replace them individually once you know which ones are more favoured.
Other
Putty rubber is a valuable item, not just for fixing mistakes, but also for masking and applying highlights. Get a rubber shaped one and also one in a pencil for the highlights.
Would also recommend some blending sticks. They just have a rubbered tip and look a bit like a brush, but allow you to soften the shading.
Fixative - just a spray can, so annoying when one of your mates puts his finger on an unfixed picture and smudges it.
The Bristol Board is probably the best thing on the list. The likes of Rymans and WHSmiths are no good for this stuff. You really need to go to a proper art shop or google it. It comes in PAD form in different sizes. Lastly, join a forum/group called WetCanvas ... is an invaluable site.
EDIT: Forgot to say, get yourself a portfolio just to protect your work, sketching can take hours and hours of your time!!
Enjoy.