Help with training my thief on maplestory?

I'm a lvl 68 and I have slot of equips that improve luk and dex, and every time I click auto assign. It tell me to put all five on to luk, so I was wondering if this is right or are you supposed to put dex = lvl x 2, like in the very beginning of the game. The character that I'm using I've had since the very beginning of the game, I've just been playing off and on. I have a base of 129 on dex but with items it equals 136 so should I keep raising dex by 2 and 3 on luk if not please tell me what I am doing wrong and what I can do to fix it.