Good, cheap WWI kits is an oxymoron. A good kit will set you back some $$$.

If you are new to building, I strongly recommend building a few slab-sided, box fuselaged trainer types before tackling the box of sticks that comprise most WWI planes kits, and get used to how to build over a set of plans and/or use photos for reference. As stated above, WWI planes aren't the easiest to fly; although they were as basic as could be, they are extremely unforgiving, and must be continually attended to in the air.

Once you have a good handle on building basics, two good WWI kits to start with are BUSA's Eindecker 40 and BUSA's Bristol M-1. Both are monoplanes and are fairly straightforward builds, and both have nice flying characteristics.

On the other hand, Polk Hobbies has a really nice looking Fokker DR-1 Triplane ARF, has a 40-something inch wingspan, and is made for electric, but will also fly on a .25 -.30 glow engine. BUT IT DON"T FLY LIKE A TRAINER.