Soooo, you are about to join the wonderful world of sock knitting. You will love it, and knitters seem to be caring and sharing.
The best pattern I have found for learning is the freebie from Lion Brand. It explains things very clearly and is an excellent basic sock pattern. You can find it online, if not on the label of some of their sock yarn.
If you cannot have wool on your feet, not even 50 percent wool, then I suggest you start with a baby acrylic, or a good nylon if you can find it. I have made at least 2 pair of acrylic socks and they are great. I throw them in the washer and dryer and nothing phases them. However, I realize I will be adding to the earth's landfill for eons when they are trashed.
One caution, I would not use acrylic socks as house socks if you have wood or tile floors as they get very slippery if the least bit damp. I almost fell stepping out of my back door because my socks were damp and slipped on the wooden floor.
100 percent cotton yarn is really hard to use for socks as they stretch out and don't hold their shape. I know from experience. I have given up on cotton unless it is in a blend with other fiber.
Check out Knit Picks for a good online store with lots of variety. You local MIchaels or A.C. Moore will also have some good selections. Some of the variegated acrylic sock yarn looks lovely.
As for dpns versus circular needles, take your pick. I learned on dpns as a very young teenager -- eons ago -- and generally have loved them and have had no problems with ladders where the 2 needles meet. However, I am an American style knitter, and by pulling backwards at the junctures to tighten the stitches I can easily control the tension. I also can knit Continental style, but find I can't control tension well when working in the round.
However, now that so many great circular needles are available, I have a great collection of those too. Just make sure that the cords are really flexible, otherwise you can have a problem when working in the round.
I am new to this site, so I think I have rambled on enough for the first time.
Enjoy your knitting, it is a lifelong sport!!!!