How long is the ffxiv main story from a fresh start?

If you play casually, budget for months rather than weeks. Something that saved me a lot of time: the free trial now covers the story right up to the end of Stormblood, so you can find out whether you like it before you spend anything.

it's long. msq only, from a realm reborn through dawntrail, you're looking at several hundred hours if you actually read the cutscenes and do the dungeons as they come up. arr is the slow bit everyone warns about, push through and heavensward picks up a lot. i wouldn't buy a story skip unless you're only there to raid with friends.