Good set for building several casual level decks
Core sets like M20 are pretty much built for this kind of "introductory" play, although if you want to represent EVERYTHING magic has to offer you might need to bleed across multiple core sets. 

I'll also say that core sets tend not to have very much multi-colour support - Return to Ravnica springs to mind as a set that explicitly encourages dual-coloured deck building, if you're willing to branch out even further.