Can you let us know what reel it is? Line size typically doesn't matter for the reel. The line #s they put on it is just so you know how much you can spool up for that given line lb test/diameter. Also, for rod ratings, yes, keeping within the ratings is great but really just setting your drag to the proper setting will allow you to use 50 lb braid on a rod rated for 12 lb test line if you just set your drag at 3-4 lbs.
Based on your limited information, I would go with 10-12 lb line and probably a braid/fluoro combo. The sensitivity over mono with this combo would be amazing and you can change your leader sizes according to conditions.
Todd