Best way to do the 2.0-2.55 Story to access Ishgard?

[Seraphyel]

The thing is, I don't want to rush through the story, but I don't want to put efforts into playing a job I am going to change. I would love to do all those stuff as Astrologian but I can't because it's locked behind 100 Story Quests which are mostly totally dumb and annoying. I understand there needs to be a requirement but the Heavensward "Gate" is awful.

I really enjoy the story with the Ascians, the Garleans and the Primae but the biggest part of the main scenario is just awful. Doing some sh*t for Tataru or going back and forth just to tell somebody that something is happening. I think I teleported 100 times the last 2 days just to get back to Minfilia... excuse me but that's neither interesting nor story-relevant.
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Another question: how do I get the job when I finish the main scenario? Can I go directly to the guild (?) and get the job when I finished the 2.55 quests or must I do more?