How well do you fly? What other planes have your built? What motors do you want to use and what kind of foam do you have access to?
Presently we are using 4 different airfoils in our marketed planes and some of the planes like the Scythe have been cut with 4 different sweep angles. We have the Roswell with a symmetrical wing, the Scythe with a thin wing, the Titan with a long fat airfoil, the Assassin with a shorter finless fat design, and the Reaper with a low drag high lift airfoil and the Snowball that has a flatfoam wing. Some of our kits have over 20 prototypes before they go on the market. Only in rare cases do the prototypes not fly at all. Our next plane will have over 40 prototype cuts before it's release.
If you are interested in trying your hand at scratch building, look at what Steve in the Philippines has done with the KF airfoil. He has done quite a few planes out of white bead foam because he can't get the EPP and he has not had a foam cutter.
In most cases it is cheaper and you get a better plane and you know what you are going to get if you buy a kit. We shipped a Grim Reaper over there and it cost about $37 USD for shipping. If you don't have the foam there it will cost you as much to get the foam there as it will to get a kit there, in fact it will cost more because you have all of the foam not just the plane parts.