how can you create 3d people and 2d people and the background
Well, there are a lot of ways you can make backgrounds and people for a game.
The easiest is perhaps to just draw them in a program such a MS Paint (though the quality isn't as high), or Paintshop pro, or Photoshop.
3D characters have to made in 3D programs, but unfortunately those programs are often both very expensive, and takes a long time to learn.
2D characters can be made in Photoshop and programs like that, but if you want animated people, you have to draw them frame by frame. Then in a program that is part of WME you put the still pictures together into an animation.
Others gone another way and made a first-person game instead. That way you don't have to draw the main character, and you might even get away with a static pictures for people instead of animations, if the game is good enough othervise.
To tell you the truth, one of the reasons I chose WME, except that it looked better and seemed easier than some of the other systems, is that it's one of the few adventure making softwares that can handle first person games. AGS can't do it, and neither can a few of the others I looked into. Then there's AGAST, but I couldn't even get it to run on my computer for some reason.
But WME was perfect.
But back to your question... If you want to make a good and solid game, there is no easy ways out. It's only your own, hard work (maybe with the help of others) that will get you there.
But don't forget, that you don't necessarily
have to have 3D characters or 3D rendered backgrounds. There is still quite a number of people who like 2D adventures as long as the game is good enough.
Oh, and here's a list of cheap and free programs:
http://forum.dead-code.org/index.php?topic=998.0