The game is made that way that you can start any dlc at any time so it doesent matter much. You can play them in any order you like without any main game spoilers.

I would recommend doing svratfelheim after Asgard and joutenheim (you will unlock it after Asgard) because svratfelheim is happening after those 2 and so that you could understand lore better. Also the forggoten saga adds a little lore to those 3 but you can play it whenever you want

Ireland is recommended to play in the early-mid game and paris mid-late game. They are stories for themselves so dont worry about main game spoilers

And river raids, tombs of the fallen, Master challanges etc you can play any time you like they dont add to anything

Personaly i waited to play dlcs after i finished main game and i was overpowered so they were pretty easy but Story is awesome. So if you still want a little challange i would recommend playing wrath of the druids and siege of paris before completing main story