Hi

I just started a new rogue character and my current goal is joining Dark Brotherhood and Thieves Guild asap, so I can finish the questlines, but the question is - how do I skip all the Imperial VS Stormcloak quests, the main quest and get invited into those guild as soon as possible?

Thanks for reading

As soon as you come out of the starting dungeon head for Whiterun and take the carriage to Riften, you will find the TG easy enough and will avoid any of the politics and Dragon stuff.

Well... start the game. As soon as you can, go to Windhelm and fulfill the kid Aventus Aretino's wish. This starts the DB. After you've done what the kid asks you to do, sleep.

For Thieves Guild, talk to Brynjolf in Riften and start the quest he offers. You may want to do this during your (presumably first) visit to Riften, since Aventus Aretino asks you to go there as well.

thanks