The Visitor Event Guide/Discussion.

can anyone explain the low medal problem.... T.T

There is no "low medal problem". The amount of Medals you get is based on your level. You can't expect them to fill up your inventory with Medals, anyways. This is really good equipment you can be making, it's understandable to get a low amount of Medals so that you can only afford 2-4 Cores a day (not including the massive amount you get at the very beginning).

I'm level 100, from the beginning quest, I got 840 Medals. From the faming quest, I got 8 Medals. From the 4 OSSS quests that you have to complete, then complete the final quest with the requirement of finishing all the other 4, I got 40 each time, since it's repeatable 3 times a day. I don't know what I get from the "Do a PQ!" quest, since I haven't yet.

Right off the bat I was able to make all 4 parts +4, and doing the 4 repeat quests twice got me enough to do 2 more cores on two pieces of the armor, so I have 2 +4, and 2 +5. So each day I'll be able to afford approximately 2-3, depending on what I can get from the PQ and how many I net from the Timer thing. Once you get all pieces of the armor to +12, though, you don't have to scroll them all evenly anymore and you can focus on whatever piece you want.

I'm quite content. On my way to +30 DEX overall and +12 STR shoes. Don't care much for the helmet or gloves.

uhm ive upgraded each piece like 7 times and they still didnt transform o.0

If you were doing it on your level 130 character, as listed in your profile thingy, then I do believe it requires you to scroll each piece 12 times for them to change, since you're 120+. I may be mistaken on this, though.