The strings I use are Earthwood Lights (9 / 42). My 12 string action is set low and play's like butter.
A little tip, when I change strings, is to leave all strings in place, and in tune, then change the standard strings one at a time. As I install a new string I will bring it to proper tune then [proceed to the next string. After I get all the standard strings changed, and in tune tune, I start changing the octave strings. I start with the 6th string octave and proceed from there. When I get to the g octave string I skip it and install all the other octave strings. The reason for skipping the g octave string is that it is the smallest string and the one most likely to break. This works for me.
As for what strings to use it depends on the guitar, the action and your ear. My advice is to try several different string sets until you find what sounds best to you and is easy to play. Lighter strings are easier on the fingers, easier on the guitar but also more easy to break. Find a set you like, get a couple of sets as backup and you are off to the races. Also, if you are out playing with a group and you break you "g" string just remove it and play your 11 string guitar. No one will ever notice,