There are number of free things you can get from the dlc’s simply by entering cities or doing part of a questline. Here is the list of these free items.
Dark Brotherhood Initiate Costume and Assassin Personality – Complete the first Mission of the Dark Brotherhood DLC
Executioner Title and Cadaverous Assassin Polymorph – Complete the Litany of Blood Achievement of the Dark Brotherhood DLC
Black Hand Robe Costume and Silencer Title – Complete the Main Quest Line of the Dark Brotherhood
“Echelette” Pet -> Enter in the City of Orsinium (Orsinium DLC City)
Four unique Recipes for Scaling Food -> Orzorga Quest Line in Orsinium DLC
Jackal Pet – Enter Abah’s Watch in Hew’s Bane (Thieves Guild City)
Master Thief Title and Coin of Illusory Riches Memento -Complete the A Cutpurse above Achievement of the Thieves Guild DLC
Thieves Guild Costume – Complete the first Quest of the Thieves Guild DLC
Merchant Lord’s Regalia costume – complete the quest “Forever Hold Your Peace” in the Thieves Guild questline.
Heroic Personality – Enter Ruins of Mazzatun or Cradle of Shadows in Shadowfen
“Werewolf Hunter Hat” from Moon Hunter Keep Dungeon or March of Sacrifices – just enter one of the dungeon for the first time and will have the hat.
Werewolf Behemoth Memento – from March of Sacrifices. Complete the Indrik Hunt achievement (have to hunt wisps, there are guides for this)
“Renegade Dragon Priest Mask” hat – enter either Scalecaller Peak or Fang Lair for the first time
“Bull Horns” emote – enter either Falkreath Hold or Bloodroot Forge for the first time
The Telvanni Magister persona can be acquired from Vvardenfell, from completing “The Heart of a Telvanni” quest.
Buoyant Armiger face and body tattoos – complete the Vvardenfell main storyline
Morag Tong face and body tattoos – complete the Balmora storyline in Vvardenfell
“Regalia of the Scarlet Judge” costume – complete the Suran storyline in Vvardenfell
“Dovah-Fly Pet” – Enter the Brass Fortress in Clockwork City
“Begone!” emote – complete “Lost in the Gloam” (part of the main storyline) in Clockwork City
“Revolving Celestiodrome” furniture item – complete the Clockwork City main storyline
“Verdigris Haj Mota” pet – enter Murkmire for the first time