I would say, if you want to keep the amount of subjob leveling to a minimum (at least to begin with)

MNK as the first sub for war instead of thf, simply because you're going to level mnk a lot faster than thf when you solo.

So, mnk18, war30, unlock sam, drg, blu. Then level sam, whm(or rdm) and blu to to 30, then drg to 60.

the reason i suggest taking the subs first to just 30 instead of 49, is that personally I get a bit impatient, and stopping at 30 for so to level the job i *really* wanted to level in the first place makes me feel a bit more content. If you have no problems staying on your subjobs all the way from 1 to 49 in one go, you can just do that instead.

After a while, you might want to unlock ninja, but in my opinion this isn't necessary in order to level blu just as a subjob, although it might help. Ninja is one of those "must have" jobs anyway, you're going to want it sooner or later, so if you feel like drg leveling can wait even a bit longer, go ahead and level that before you start seriously leveling drg as well.

After DRG60, i would keep continue leveling my subs to 49, and then take DRG to 90.