I started with 10mm wooden ones from the market and acrylic yarn. The needles were fine for a few weeks, particularly because the stitches didn't slip off while I was learning but I got frustrated with it the more I practiced because my knitting got tighter and I couldn't move the stitches off the wood very easily so I switched to aluminium. Its all a matter of preference. I wouldn't start with anything too small though.
"If you'd been listening, you'd know that Nintendos pass through everything" - Jack O'Neill, SG-1