The most important one at lv 90 will be ninja. war and dancer have their place, but you will most often find yourself /nin.
You can do something like:
Mnk> to 18~24ish (unlock subjob)
War/mnk>49 (unlock advanced jobs etc once 30. Get familiar with how stuff works, make some money etc)
Dnc/nin>49 (Dagger will be skilled up and waiting for you at thf 33 so you can use sword/h2h on thf at low levels)
Thf>90 (/dnc for solo, /war or /nin for party etc)
That would be my sorta 'ideal' path. You will never have to backtrack to do subjobs, you will have them all available for thf, but this is just an optimized deal. But of course were people not robots. That is a rather long time to wait to even start playing your desired job.
With that in mind, so long as you level those at some point, you will be fine. You just might have to backtrack and finish off subjobs at a later point which is annoying, but not the end of the world. Sometimes you need that change of pace anyway.
Aanalaty, Mithra of San d'Oria
99Thf/99Drg/99Rng/95Pld/Secret Job 92
Maat-1/1 Thf Meleed (pansies steal)
Some of mah gearz: http://www.ffxiah.com/player/Lakshmi/Aanalaty#item-sets
Join 'People Against The Heart Snatcher' and help put Thfs on the right P.A.T.H.S.