I know this isn't the CB approved "play lich forever" learning method, but when I started playing dota 2 (I'd played dota 1 some but not in forever), I basically went through and did fake A-Z. For context Wellie: A-Z is when you play every hero alphabetically until you win once with each guy. I just did one game each, but like you said, for me knowing what other heroes are able to do to me is very helpful when playing, so being able to run through and get a sense of the rest of the roster was helpful. Takes fucking forever, though. The probably (easiest) way would be to work through in this order: http://www.dotabuff.com/heroes/played since they're the ones you're most likely to encounter in games. It's kinda shitty that pudge/invoker are top 2 though, since they're 2 of the least newbie friendly heroes.