Ragnarok.Jessikah said:
»Go out, actually fight monsters, learn the job, skill up naturally.
I'm actually not even just trying to be a jerk here, Blue Magic skill levels extremely quickly if you cast it on enemies. Even if you partied in Abyssea, I wouldn't doubt you'll be getting your skill capped (or close to it) in between each level.
Jess is right...BLU magic skill is relatively easy to skill up. Just cast spells that don't get resisted (breath spells).
I personally skilled up on the worms in Aby-Ule on BLU/Whatever. Just get a refresh atma and some magic acc atma and spam spells on them (cursed sphere/bomb toss/sandspin worked really well for me for some reason)
Blue skill will get up to near cap in no time. Then just finish it off in exp parties/everyday stuff.