I actually started from scratch and did quite well the first time around. I used these plans the first time around - obviously they are quite a bit dated and definitely can be improved upon - but they will allow you to make a plane that flies easily a minute to a minute and a half.http://webs.wichita.edu/scienceolympiad/ws/ws.html
I learned from there and started adapting to my own designs, eventually going to mylar covering (although I switched back to tissue) and eliminating the wing saddle (although it was great for a first time flier). But it gives you the technique and advice to start.
You'd probably fare a little better time-wise by starting with a kit, but in my opinion that takes the fun away from it, and you learn a lot less. Building from scratch will result in lower times initially, but if you're patient enough, you can do just as well. Eventually, you'll be able to trim your planes better than a kit one, and you'll probably be able to fly longer.
Sure, you can go out and buy a Dave Zeigler kit. From what I've seen, they do fly very well. But don't expect to get 3 and a half minutes the day you build it. It takes a lot of practice to trim the plane. You can get the same results from scratch, but it's more difficult to begin with, even working with a set of plans.
WS is not an expensive event. I think the most expensive thing was the rubber - and if you buy enough it'll last you many, many airplanes.