Dawnguard is a great DLC that I would definitely recommend especially because of the new weapons and werewolf/vampire revamps, as well as adding cool new places and NPCs, like *quest spoiler alert* Dragonborn is pretty cool as well because it's a whole new area to explore, with lots of big juicy quests. When it comes to Hearthfire, it is really only for people who like immersion and building your own house, I own it and it's enjoyable but if you just like fighting then it won't be for you. Above all, I would recommend all DLCs, Dawnguard would take precedence if you like the new weapons and werewolf/vampire revamps, Dragonborn would take precedence if you like the new lands, whether or not to get Hearthfire depends on your personal taste.