ArDanZ11 Then you should make a tetris clone first.
Besides, you don't need to be "good enough" to participate in a jam. Enter one and see what you can make. The purpose of jams is to have fun, sharpen your skills, learn to deal with procrastination and perfectionism, and in a short period of time produce something that looks like a complete game, however small or simple it is. That last bit is particularly good for developing self confidence.
