I generally go with the old classic the Cortland 444 peach double taper. Have been getting the Hook & Hackle olive DT lines lately since they are half the price of the other brands and cast roughly the same as the Cortland peach.
At my regular dry fly distance I'm not sure double taper or weight forward makes any difference. However, you can switch ends on a double taper and get twice the life. Due to cutting tolerance, the thin part at the head of the line is often a touch long. If you find your line isn't turning over nicely and the front seems to be a constant thin diameter for some length, cut it down to where the taper starts.
Most reputable companies make a decent line these days, so I frequently check out the bargain bins at fly shops. Royal Wulff, Rio, Scientific Anglers have good lines. Be careful though. The bargain bins are filled with weird specialty tapers (just get a basic floating DT or WF IMHO for trout dry flies). The fly fishing industry always has to have the latest and greatest to get us to buy new lines. Most of these end up in the bargain bin while the classic floating DT or WF Cortlands, Rios, Scientific Anglers, etc never seem to go out of style. Ramsey Outdoors recently had a lot of good lines in the sale pile - but they seem to getted picked over more each day.
Get a decent line - it is more important than the rod.
Finally, you will hear endless arguments over color. I'm not sure it makes a lot of difference. However, PA limestone guys I respect go with dull shades of gray and olive for camoflage. Other guys like the bright oranges and chartreuse to follow the line. For dry flies on trout streams I like muted colors like peach, tan, and olive just because it looks right to me. Fly fishing doesn't always have to make sense.