...or depend what your goals are when You are at your current level during the Moment in wich you are playing .
However , normally I think a good set could be : Hp potions , minor shield potions ( of you are playing as a rogue , I guess you have Grissenda or Hirge as a tank purpose companion , so providing them extra protection means privide that to you too at the same time , expecially when you are LV 15 Rogue ), potions of agility ( of you are fighting a rumor boss or a mob with hight Attack and your companion Is down ... You really want extra Speed ), some scrolls for detect hidden elements ( if you go in a dungeon you never bene before , they could be helpful )