I like the RIO brand, but i think the others you might try will be good also...Umpqua, Frog Hair, Dai Riki and Climax are just as good...but for some reason the RIO ties better for me. If you havnt used flourocarbon before make sure you wet your knots with saliva before you tighten them and also make sure your knot dresses up properly...its does not tie as easy as regular mono and you really have to pull them tight. flouro is more abrasion resistant than mono, and thinner on average compared to regualr mono of the same weight strength...plus it doesnt stretch as much. its denser than mono, so i use it only for nymphs and streamers, as it sinks quickly.
usually a spool of flouro will cost you between 10 and 14 dollars....i think the umpqua is the cheapest at around 9.95.