Probably enchanting weapons with holy water from the sparks npc.
e.g,
Holy Water (51) -- from 50 to 62
Holy Mace (55) -- from 62 to 66
Holy Maul (71) -- from 66 to 82
Holy Wand (81) -- from 82 to 92
Ice Shield (97) -- from 92 to 108
NPC everything you make. The holy water can probably be made for around ~500gil each (depending on your server), and I imagine this is a healthy way to get rid of your unneeded sparks.
I haven't done this myself, but I think it's probably better than doing the traditional route of anima, hi-ethers, pro-ethers, etc, which are probably outdated now.