if you have easy access to lightning crystals, buy flax flowers from the guild shops at about 200 gil a flower... 1x lightning crystal+ 2x Flax flower=1 linen thread... cheap.even if you have to buy the lightning crystals, its waaaay cheaper than buying the linens to make these. but i agree with Tsu, you can just make Heko Obis until you can make Shinobi-Tabi...
Im not quite sure on the skill u should be but try sumthing like 25-26 and youre right it does sound pretty cheap to level on. look for next post to see prices.