I guess comes down to how much play time you have. From say level 1-50 it really does not take all that long, but highly suggest to find a Free Company and friends to help you out.
Some of the older content players just do not do as much anymore.
Fates, dungeons, hunting log, Free Company exp buff and also eat experience food all help oh and leves if you absolutely need.
End game raiding like say Alex Savage and Thordan EX most definately could be tough to actually complete just with pugs, but a dedicated group should be no problem.
You do have various Primals first to do, regular versions, Hard Mode versions and then Extreme versions of Primals, all of which (with exceptions to the battles in Heavansward) can be done unsynched and undersize parties. Which basically means instead of the usually 8 players you could do it with say 3 or 4 (or less) but with the higher level gear and abilities.
Heavansward is worth getting but you can also wait until you are close to having the 2.x storyline complete.