grab about four stacks of lightning crystals. sit ur *** down in jeuno jewery shop buy a bunch of silver earing and start desynthing at lv 25. ull fail some but ull HQ some 2. then start ur hair pin then desynth all those hairpins. onc eur around 28 29 or so desynth rings from same shop. even if u lose four earings, ingots stacks are goin about 36k+ so it can still pay for itself. plus its a super super easy way to make easy gil and all u had to spend is about 24k at the most if you didnt farm crystals ur self.
I have been using this up to level 30 WHM... the trick is to use the Doublets (which compared to the Tunics, dont give you the INT bonus, but as a WHM, who needs int anyways?) which will allow you to use a headgear. This nice boost of MP greatly helps your casting, and if your pty is good enough, the minus hitpoints are not bad. Toss in a couple of Astral Rings (if you can afford them, of course) or even Onix earrings, and you will feel the difference...
its nice for a mage who doesnt wear a tunic such as a rdm around 21 who has bettle gear or whm's with a great doublet..i use one at my 24 rdm with the doublet equipment and these haipins give a nice boost of mp since rdm's naturally have low mp than other mages