Good set of cards for teaching beginners
I would not recommend any one card set to teach all the important rules from each expansion.  That may be too much.

For brand new beginners, I recommend the "Big Money" set from the first game.  I use this before the one recommended by the base set rules ("First Play"?) because it teaches the trade off between money and actions.  First Play is really a preview of all the different card abilities, which may give the erroneous impression that the game is all about actions.

Otherwise, I'd play random sets (with some drafting) from the combined sets and teach the rules as they come up.