Do/Should you be at a certain point in the main quest or Dawnguard before you start Dragonborn?It might be a stupid question just know in dawnguard you had to have the elder scroll didnt know if somethin like this was needed before i start to play.Thanks

Up to the part were you have to get the horn of jurgen or whatever it's called, just before you meet delphine.

You will get certain extra dialogue if you complete the main quest but you need to have completed the horn of jurgen windcaller quest to gain acess to the Dragonborn main quest.

Complete the Horn of Jurgen Windcaller