If you're a little confused about what spey line to buy, your not alone. It's not an easy thing to figure out.
So your interest in spey fishing has accelerated to the point where your ready to get some gear. Not so fast. Guys have spent piles of money on rod and line combos that just don't get the job done. I can't tell you exactly what line will work with a certain rod for a specific situation, because the possibilities are many. What I can do is help narrow the selection. Things can become quite confusing when you get into details about line length and tapers. I'll try to keep things short and simple. First you need to know what flies you will be fishing, how far you intend to cast them and what depth you'll fish them at. This will tell you what fly line and rod you will need. I'll cover the three types of spey lines available. Standard spey lines, Skagit lines, and Scandinavian lines.

Standard spey lines are designed to be used with two handed rods. They come in varying head lengths to accommodate the distance you will fish at most. Head lengths range from about 45 to 100 feet. Older line designs were basically an oversized weight forward line. Modern spey lines have more weight toward the back of the head which will make it easier to form a loop behind you during that part of the cast. A shorter head will be easiest to handle and learn with for beginners.

Skagit lines are quite aggressive and used to cast big flies and heavy sink-tips at closer ranges. These lines are available for single or double hand rods. They were first available as shooting heads, but now I also see them as a full lines with running line attached. The head lengths are usually around 20 to 30 feet long and work well in tight situations. Your casting does not have to be perfect with these lines. If the line does not anchor in the ideal position during the cast or your timing if off and you end up with more line on the water than there really needs to be, the mass of these lines will often negate these errors and still deliver the fly to the target.

Scandinavian lines were designed for the Scandinavian style casting where only the fly and leader touch the water on the anchor. Timing of the cast is more critical, but with less line contact on the water during the anchor you are able to cast farther. The head on this style of line is a little lighter and longer than the Skagit. About 30 to 40 feet. They have a longer front taper which is lighter near the tip and heavier near the back of the head. This allows for a more delicate presentation. This line is better for when you need to present smaller flies at longer distances to fish that are easily spooked. These were first available as shooting heads, but I see them as full lines now. They are available for single or two handed rods.

Most of the lines I talked about are available with interchangeable tips with different sink rates to get your fly to different depths. The things I've mentioned should help narrow down your choices. The next step is to find someone that fishes in the exact manor that you will be and find out what rod and line combination works for them. Doing the research will save you a pile of money.