Yes start building more kits first, in the meantime if you have an idea for a design that you would like to try building down the road. Try a program called Metasequoia,
http://www.metaseq.net/english/index.html it is a free and easy to use and learn polygon modeller that can be used to create a concept model of your plane. I use this when i have an idea for a plane and want to create a 3D model quickly, which you can then tweak and redesign to your hearts content.
Also learn a CAD program, they can be a much more powerful drawing tool than pencil and paper. TurboCAD is a good one for newbies to learn. It is the one i use for drawing. TurboCAD V7 or later preferably.
Here's a couple pics of a model that went from Metasequoia to TurboCad to an actual RC aircraft that was built in 2 sizes.