Binding of Isaac is a marvelous game. It feels like it shouldn't be, but I probably sunk 80+ hours into it, and I've not even touched the DLC.
Since you've already hit it pretty hard, I would add the DLC, it adds lots of Fun to the game. It does make performance take a major hit though, because of the way the developers used Flash.
My other piece of advice is: don't get spoiled. Don't read about the enemies, levels, powerups, etc. online. Just play the game and let it teach you.
I cannot find any source to this, so please someone who played, correct me.