Re: Help Needed..New setup
Your reel will take about 220 yards of 30 lb Dacron or Micron backing plus a weight forward 10 weight fly line.
As far as fly lines go, I've mostly used various Scientific Anglers Mastery lines (about $70) so can't rally comment on others for SW. There are a ton of choices, even in this family of fly lines-- floating or sinking, weight and coatings. Saltwater fly lines are generally stiffer than the fly lines used in freshwater to stand up better to wind and deliver large flies.
For new caster, I think I'd recommend a floating line. A floater will be helpful for fishing shallow water for redfish, and would be good for snook in shallow water as well. You can also use a floater for mahi especially if you're sight casting to them in weed lines, or have teased them to the surface. And for a 10 weight rod I'd get either a 10 weight or 11 weight line. (Over loading the rod with a bit heavier line might help a bit as you're learning to cast.)
Depending on where you're fishing you'll want a fly line that doesn't get too gummy in intense tropical heat (like a SA Mastery Tarpon Taper) or turn into a wire slinky in cold water and fishes well in a variety of temperatures (SA Salt Water Mastery).
I'm sure other fly line manufacturers like Rio and Air Flo have similar offerings and there are probably a variety of less expensive lines that would work too-- i just don't have experience with them.
If you have a local fly shop, you could perhaps try a few lines to see what works best with your outfit and buy a fly line from them and have them rig it all up and put the backing on for you (about $ .08 a yard). A local shop might also offer some casting lessons for a nominal fee to help get you started.
Keep asking questions-- we have a lot of members here that can give you great advice.