Originally Posted by
Nyarlko
Abyssea is your friend for learning blue magic. 15min or forced repops aren't bad for the NM-only spells, and the bestiary covers quite a large chunk of learnable families. If you are not done w/ Abyssea, now's a good time to go (since boosted lights and easier to get KIs along the way,) and you will need to finish it to have access to Mighty Guard.
Assuming you have a solid 119 job of some sort, quite a few spells are available from Geas Fete NMs, many of which are solo/lowman-able. Legion also works for a number of 'em (though the hydras don't use Pyrhic Bulwark) and is dirt cheap to enter nowadays.
Suggest you track down all the dual-elementals and learn all 8 of their spells as they are very strong and have good traits attached. Alluvion Skirmish Yorcia Weald w/ a 1/1/1/cape entry KI will give you a level where all the mobs are elementals, including some of the duals. This is the most reliable way of learning their spells since weather is never actually predictable in-game.