I am by no stretch of the imagination an expert so I'm not sure I should actually be answering you!
Having said that... I am currently working with an absolutely fabulous yarn! It's called MerLin Tristin and is 100 gram Sport Weight. 40% Merino 60% Linen It's a bit pricey but a skein is 250 yrd. and it is machine wash and dry
!!! I just love this stuff and it does not split like other sock yarn I've used! I'm using size 3 needles and the socks are coming out perfect.
And I second everyone's suggestion to use a heavier yarn for your first pair. It helped me tremendously to do this becasuse I could actually see how things worked and came together.
Good luck with whatever you decide!