What line for a redington redfly 12'6" 7/8 spey

I just got my fist spey rod [used]and need help on deciding on what line to get. I got a redington redfly 12'6" 7/8 spey.I will be fishing for trout with drys and some streamers. I don't think I will be casting over 90'.I do tend to use long leaders [12-18']and light tippet 5x,6x. I was thinking of a multi tip system. floating and sinking tips. I would like to know my options. Also would someone explain to me why , someone would pay $700 for a reel when you can but a disk drag reel for $35? Any and all thoughts will be greatly appreciated. Thanks Steve