Joni if you being 13 keep that enthusiasm about video editing, watch online tutorials, read, experiment, and go to school for editing, I'm sure you'll become a great editor in no time.
Since I'm a newbie I can only answer the following
The Green Screen which is used for Chroma Keying, can be achieved by buying green fabric to use as background and making sure that the subject in front of the fabric is not wearing any similar tone of green, and also using proper light to avoid shadows. Then you need the editing software to have the Chroma Key option.
About cheap effective video editing software, I have no idea, I know people use Pinnacle, Windows Movie Maker, but I don't think those will work for Chroma Key effect nor the Lightsaber effect. I am sure some of the experts here will be able to suggest a better option.