As Corpse Fool said: probably subscription is the best answers for Your question

every DLC's give something interesting: content, mechanics, etc without I cannot imagine my games. If I'm not mistaken, even TFTV, which has very basic, oldfashioned focus trees, gives You oportunity to manage Your pupetts (correct me, if I'm wrong, I don't remember the older DLC's very well and I cannot check it now). HOI4 without DLC's is still playable, of course, but it seems like a demo
I like the subscription idea - I don't use it, because I have all DLC's, but this is a good options to check content and mechanics for new players.