The most valuable plug-in you can ever have: Your brain. Seriously, simply do a web search for tutorials. There's enough from "Harry Potter" fights to any kind of magic portal effect. None of what you describe per se requires any plug-in nor is there any "magic" plug-in that would produce all this stuff at a single mous click.
Best advice as Mylenium says is to look at as many tutorials as you can - I'd start with the excellent and fully featured tutorials from www.videocopilot.net and also http://library.creativecow.net/tutorials/adobeaftereffects
Getting to grips with particular will also give you some creative options with particles.