Since your a beginner, I suggest using Windows Movie Maker. It's easy to use, has some decent effects and transitions and...if you have a PC... it's free! The more confident you get at making movies, you can upgrade to a more professional program like Sony Vegas, or Adobe Premier..but you have to buy those programs and some of them can get pretty pricey... unless your willing to *cough*illegally*cough* download them... If you need any help using Movie Maker, just PM me. I'm always willling to lend a helping hand to fellow AMV makers. ^^
I use Windows Movie Maker my self. I know that it doens't have alot of effects but what it does have is pretty good...if you want to use a different program though, I can PM you a way to get Sony Vegas 5.0... As for uploading your AMV's... I'm pretty sure I know what the problem is. You might be trying to upload the Movie Maker project file...instead of the movie file. To save your finished project as a movie file is very simple. Go to File> Save as Movie File... than just choose the saving location and click Save. Once it's saved it should be uploadable... but if thats not the problem I don't know how to help you...
I use Windows Movie Maker for my vids right now... But I recently downloaded Song Vegas 5.0 so I'm gonna try and use that after I'm done my next few projects.