Someone else mentioned rushing a character through the game, so thought I'd put this out there.
In-game time totaled to 3 days, 10 hours, but maybe 6-8 of that was time spent afk. I spent about a month playing on the character though, but I would hope you wouldn't assume that I just casually ran through the MSQ like that in 3 and a half days straight. The hours are a bit uneven over the month since there'd be times like today where I spent 8 hours on the character(unhealthy I know, but I just finished my last final for this semester this morning and I was in a really good mood).
The character was made on Dynamis for the road to 80 buff. I started CNJ, grabbed SAM at 50, DNC at 60, RPR/SGE at 70. Played as WHM through HW(did all job quests up until that point), and around that point I hit level 70 so I grabbed SGE. Did all the SGE job quests for Panhaima which took about an hour too. I probably didn't need it, but I didn't want to be that person(that's a lie, I needed it for SoS and literally every level 80 dungeon because my teams kept running through every resource I had). You can create keybinds for each class, and I'd usually have one for my healing class and one for my DPS class or one Healer along with one for RPR + one for DNC(for Pelo).
I only did 4-5 levelling roulettes and around the same for MSQ. The gear from SGE/RPR overgears your left side for SB and below. I probably should have checked the MB for cheap upgrades but I didn't bother until level 80.
Generally I tried to use trials from HW on and as check points. I queued for everything as a healer, and I never had a dungeon queue over minutes. I never had a trial queue over 10 minutes, but I believe that's because I did my best to do my msq trials either around reset time or in the evening.
Oh and for solo instances, if you can die at the beginning really quickly you can use that to get access to "very easy" mode to maybe speed up the quest. If you can't or if you know the instance is tied to a story line then it's not worth it.
The character ended with around 1,500,000 raw gil from progressing through the story line. 100,000 of it was spent on cheap level 80 upgrades.
You could probably do this way better than what I did.
I actually had a plan with this in mind but it's just way too tedious. The only reason I really finished this character(or at least finished getting it to the goal) was mostly because I started it. Obviously don't do this as a regular player, and probably don't do this on an alt either unless you're really curious.