Can someone explain to me what the main purpose of leaders are? Also what do most of you guys use for backing? Do you always use a leader or do you spool straight mono/fluro/braid? I am confused and wondering what I should do. It doesn't make sense to spool my bait caster with a new spool of seaguar invisx that costs $20 to have it replaced with another spool in 2 weeks. Any tips or info would be great.

Having braid as a main line and fluorocarbon leaders does a couple things for me

 

-Saves money, because braid can last for several seasons without having to be replaced. You can buy the filler spools of fluorocarbon and use that as a leader material. A 200 yard spool can last quite a while.

 

-Gives you strength of braid with the invisibility of the fluorocarbon 

 

-Shock absorber 

 

I back my reels up with braided line, but cheap mono will work as well. I spool around 50 yards of 12 lb mono diameter on my reel that holds 120 yards.

There is no right or wrong way, just preference.  I only use spinning gear and I don't use backing, I do use braid and leader always.  I like some shock on heavy strikes like on a top water but jigs or plastic worms not so much.  A leader can break a too large to handle fish off, or breaking off a snagged lure easier than straight braid.  Getting braid tangled in a treble hook can be time consuming unraveling it, much faster with a leader.