I use local organic, grass fed whole milk, but I think you can pretty much use any milk you like. I have read, however, not to use ultra-pasteurized or high pasteurized milk – something about it not feeding the kefir grains properly, as most of the nutrients have been ‘pasteurized’ right out of the milk. I have not tried this out.
I have not used raw milk, and my kefir comes out great, so I wouldn’t worry about finding raw.
Keep in mind if you’re just starting out – it will take a few batches for it to come out right (I had to dump my first 4-5 batches) – I am told the grains need to become accustomed to their new environment before they produce kefir you actually want to drink (early batches for me were super yeasty and kinda gross).