Bring your battle armor to level 18 and rank 3 at least, that's the very minimum for you at your level (i think at least 3-4k of the power you miss is there).
After that, as said 'sop...gmail', gather as many low level refinement runes as possible and use all of them in a row when there's a refinement rebate.
So, what you have to do is the following:
Buy as many low level refinement runes as you can in ranking shop and bring one piece of equipment per time to rank 4 when there's the rebate, buy all the common threads you need in monthly event shop and level up your battle armor rank when there's battle rebate and do every week all the SA difficult possible to get the highest number of medium and advanced clothes needed. if needed change main to water to make it easy for the day you go for it.