Needle size help

Hello! Beginner knitter here: I’d like to knit my first pair of socks, but I’m a bit torn or not feeling confident about the needle sizes.

I unfortunately can’t spend too much money on knitting equipment, so ideally I’d like to buy just one pair of needles that I can knit lots of socks with; should I choose:

1. size 2.75 mm or 2.25 mm?

2. 9” circulars or 32-40” circulars?

For context: I currently have the Patons Kroy sock yarn and already swatched in 2.75 needles, which gave me a satisfying 64 st cast on. I need new needles because I didn’t know those were the wrong length (16”), so I was unable to knit in the round or even do a magic loop. My bad!

For this reason, I’m thinking of sticking with the 2.75 mm needles since I already checked my gauge with them. But I’m open to advice for both needle & cable size of course! Thank you in advance! 😁